Pagola, S Benavente, A Raschi, A
Romano, E Molina, MAA Stephens, PW
Crystal structure determination of thymoquinone by high-resolution
X-ray powder diffraction
AAPS PHARMSCITECH 5, 2004, 28
The crystal structure of 2-isopropyl-5-methyl-1,4-benzoquinone (
thymoquinone) and its thermal behavior - as necessary
physical and
chemical properties - were determined in order to enhance
the current
understanding of thymoquinone chemical action by using
high resolution
x-ray powder diffraction, Fourier transform infrared spectroscopy
(
FTIR), and 3 thermo-analytical techniques thermogravimetric
analysis
(TGA), differential thermal analysis (DTA), and differential
scanning
calorimetry (DSC). The findings obtained with high-resolution
x-ray
powder diffraction and molecular location methods based
on a simulated
annealing algorithm after Rietveld refinement showed that
the triclinic
unit cell was a = 6.73728( 8) Angstrom, b = 6.91560( 8)
Angstrom, c =
10.4988( 2) Angstrom, alpha = 88.864( 2)degrees, beta
= 82.449( 1)
degrees, gamma = 77.0299( 9)degrees; cell volume = 472.52(
1)
Angstrom(3), Z = 2, and space group 1 (1) over bar.
TREOR
2004-2
Gomez, A Rodriguez-Hernandez, J Reguera, E
Unique coordination in metal nitroprussides: The structure of
Cu[Fe(CN)(5)NO] . 2H(2)O and Cu[Fe(CN)(5)NO]
JOURNAL OF CHEMICAL CRYSTALLOGRAPHY 34, 2004, 893-903.
The structures of copper pentacyanonitrosylferrate dihydrate,
Cu[Fe(CN)(5)NO].2H(2)O, and anhydrous, Cu[Fe(CN)(5)NO],
have been
determined from their XRD powder patterns and refined
using the
Rietveld method. The dihydrate structure was solved by
direct methods
and the anhydrous one was elucidated by chemical intuition.
Cu[Fe(CN)(5)NO].2H(2)O is orthorhombic, space group Amm2
(38) and Z=2.
In this structure the iron is coordinated to five CN and
a NO ligand,
while the copper atom is coordinated, in a unique fashion,
to four
equatorial CN groups at N ends and two water molecules.
Cu[Fe(CN)(5)NO]
is tetragonal, space group I4 mm (107) and Z=2. This structure
is
obtained from the dehydration of the orthorhombic one;
reordering
allows the Cu atom to coordinate not only to the four
equatorial
cyanides but also to the axial cyanide. The coordination
of the iron
atom remains as in the orthorhombic structure. Agreement
factor
obtained from the final refinement were as follows: R-wp=5.10
and
R-B=4.57 for the orthorhombic structure and R-wp=6.52
and R-B=7.82 for
the tetragonal one. These crystal structures are also
supported by IR
and Mossbauer spectroscopic data and thermogravimetry.
TREOR
2004-3
Vivani, R Costantino, F Nocchetti, M
Gatta, GD
Structural homologies in benzylamino-N,N-bis methylphosphonic acid
and
its layered zirconium derivative
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 4013-4022.
A new layered zirconium diphosphonate fluoride, ZrF(O3PCH2)(2)NHCH2C6H5
has been prepared and its structure determined ab initio
by X-ray
powder data and refined with the Rietveld method (orthorhombic,
a =
8.9429(2) Angstrom, b = 9.1746(2) Angstrom, c = 31.5654(7)
Angstrom,
space group Pbca, V = 2589.9(1) Angstrom(3), Z = 8, R-wp
= 0.080).
TREOR, DICVOL
2004-4
Atkinson, TD Fjellvag, H Kjekshus, A
Synthesis, structure, and properties of chromium(III) sulfates
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 4351-4358.
Reactions between CrO3 and 50-95 wt% H2SO4 are studied at temperatures
up to the boiling point of the acid. Depending on the
H2SO4
concentration and synthesis temperature, Cr-2(SO4)(3),
CrH(SO4)(2),
(H3O)[Cr(SO4)(2)], Cr-2(SO4)(3) . H2SO4 . 4H2O (gross
formula), and
(H5O2)[Cr(H2O)(2)(SO4)(2)], are obtained as identified
reaction
products in addition to the incompletely characterized
chromic-sulfuric
acid. The Cr-III-based sulfates are characterized by X-ray
powder
diffraction, thermogravimetric, and magnetic susceptibility
measurements. The nuclear and magnetic structures of Cr-2(SO4)(3)
at 10
K are determined, the structure type of (H3O)[Cr(SO4)(2)]
is
established, and the crystal structure of (H5O2)[Cr(H2O)(2)(SO4)(2)]
is
firmly stipulated.
TREOR
2004-5
Chernyshev, VV Stephens, PW Yatsenko, AV
Ryabova, OB Makarov, VA
Structural characterization of prazosin hydrochloride and prazosin
free
base
JOURNAL OF PHARMACEUTICAL SCIENCES 93, 2004, 3090-3095.
three-dimensional solid-state structures of prazosin hydrochloride,
C19H22N5O4+ . Cl- (A), and prazosin free base, C19H21N5O4
(B), have
been determined by synchrotron X-ray powder diffraction.
A and B
crystallize in triclinic P-1 and monoclinic Cc space groups,
respectively, with one structural unit per asymmetric
part. In A and B,
the prazosin molecule adopts different conformations,
which do not
correspond to those obtained by DFT optimizations of protonated
and
free prazosin.
TREOR
2004-5
Cremer, U Disch, S Ruschewitz, U
CaCu(C2H)(3) . 6 NH3 and Rb2Cu(C2H)(3) . NH3:
Two
ethinylocuprates with a trigonal planar [Cu(C2H)(3)](2-)
anion
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 630, 2004, 2304-2310.
By reactions in liquid ammonia Ca[Cu(C2H)(3)] (.) 6 NH3 and
Rb-2[Cu(C2H)(3)](.) NH3 were obtained as polycrystalline
solids. The
new compounds are very sensitive against loss of ammonia
and are only
stable in a NH3 atmosphere at room temperature. Structural
investigations based on X-ray powder diffraction data
resulted in
hexagonal unit cells (Ca[Cu(C2H)(3)] (.) 6 NH3: P6(3)mc,
Z = 2, a =
986,39(1) pm, c = 926,47(1) pm; Rb-2[Cu(C2H)(3)] (.) NH3:
P6(3)/m, Z =
6, a = 1096,46(2) pm, c = 1600,15(3) pm).
TREOR
2004-6
Fantin, G Fogagnolo, M Bortolini, O
Masciocchi, N Galli, S Sironi, A
Structural and analytical powder diffraction studies of the
enantioselective inclusion of chiral arylmethylsulfoxides
in
dehydrocholic acid cocrystals
NEW JOURNAL OF CHEMISTRY 28, 2004, 1295-1300.
Dehydrocholic acid (DHA) has been employed in the separation of chiral
arylmethylsulfoxides through selective precipitation of
highly enriched
1 : 1 cocrystals of p-XC6H4SOMe@DHA (X = Me, OMe, Br,
H) formulation.
X-ray powder diffraction (XRPD) has shown that two, nearly
isomorphous,
but distinct classes of compounds are obtained. Their
complete
structural analysis has been performed by ab initio XRPD
methods.
TREOR
2004-7
Ivashkevich, LS Lyakhov, AS Selevich, AF
Lesnikovich, AI
Crystal structure determination of In-3(H3O)(H2PO4)(6)(HPO4)(2)center
dot 4H(2)O from X-ray powder diffraction
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 219, 2004, 543-547.
The crystal structure of indium hydrogen phosphate hydrate,
In-3(H3O)(H2PO4)(6)(HPO4)(2) . 4 H2O, has been determined
from X-ray
powder diffraction data by using direct methods (EXPO
program), and
refined by FULLPROF package to R-Bragg value of 5.6%.
The structure is
monoclinic, space group C2/c (No. 15), unit cell dimensions
a =
17.0835(5), b = 9.6795(3), c = 17.8776(4) Angstrom, beta
=
90.301(2)degrees, V = 2956.2(1) Angstrom(3), Z = 4, D-x
= 2.73 g/cm(3).
Hydrogen atoms were placed on calculated positions. There
are two
unique indium atoms in the crystal structure. InO6 octahedra
are
connected together via the corners of PO4 tetrahedra to
form layers
parallel to the xy plane. The layers are linked to-ether
by water
molecules, located in the interlayer space, through their
hydrogen
bonds. Within the layers there are hollows occupied by
oxonium cations.
The compound was found to be isostructural with salts
of the
composition M-III M-3(I)(H2PO4)(6)(HPO4)(2) . 4 H2O, where
M-III -
trivalent metal, M-I - monovalent metal, oxonium or ammonium.
TREOR
2004-8
Robins, ELR Brunelli, M Mora, AJ
Fitch, AN
Low-temperature crystal structure of RS-thiocamphor
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 219, 2004, 580-583.
DSC and high-resolution powder X-ray diffraction measurements in the
range 295 K-100 K show that RS-thiocamphor undergoes two
phase
transitions. The first, at around 260 K on cooling, is
from the
room-temperature body-centred-cubic phase to a short-lived
intermediate. At 258 K the low-temperature form starts
to appear. The
crystal structure of the latter is orthorhombic, space
group Pbnm, with
a = 9.0643(4) Angstrom, b = 14.6714(8) Angstrom, c = 7.2878(4)
Angstrom, Z = 4, rho(calc) = 1.15 g cm(-3) at 100 K. The
structure is
twofold disordered, with the enantiomers superimposed
in the average
structure, related by the mirror plane.
TREOR, Sync
2004-9
Mathieu, Y Paillaud, JL Caullet, P
Bats, N
Synthesis and characterization of IM-10: a new microporous
silicogermanate with a novel topology
MICROPOROUS AND MESOPOROUS MATERIALS 75, 2004, 13-22.
A novel GeO2 or (Si,Ge)O-2 zeolite phase called IM-10 was obtained
in
the presence of the well-known hexamethonium ion as template
and in
fluoride media, from gels with Ge/Si molar ratios greater
than or equal
to 1. With decrease of the Ge/Si molar ratio, BEC-type
zeolite and
ITH-type zeolite were successively obtained. The recovered
IM-10
samples were characterized by X-ray diffraction, SEM,
elemental and
thermal analysis, F-19 MAS and H-1 liquid (after dissolution
of the
samples in HF) spectroscopies. Due to the small crystal
sizes (1-4
mum), the structure was determined from powder X-ray diffraction
(of
the GeO2 as-made sample) and refined by the Rietveld method.
IM-10 is a
new member of the clathrate family. It crystallizes in
the tetragonal
symmetry, the space group being P (4) over bar n2. The
framework is
made of F--containing D4R units, bridged by GeO4 tetrahedra.
The
arrangement of the D4R units creates [6(20)4(2)] supercages,
each of
them occluding one hexamethonium cation. Structural similarities
exist
between ASU-9 (AST), ASU-7 (ASV) and the new IM-10 zeolite
with a novel
topology (UOZ).
TREOR
2004-10
Ma, HW Liang, JK Wu, L Liu, GY
Rao, GH Chen, XL
Ab initio structure determination of new compound Ba-3(BO3)(PO4)
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 3454-3459.
Ba3BPO7; borophosphate; structure determinations; x-ray powder
diffraction
The crystal structure of new compound Ba3BPO7 was determined by ab
initio method from high-resolution conventional X-ray
powder
diffraction data. The Rietveld refinement converged to
R-p = 5.92%,
R-wp = 8.87%, R-exp = 5.00% with the following details:
Hexagonal,
space group P6(3)mc, a = 5.4898 (1) Angstrom, c = 14.7551
(1) Angstrom,
Z = 2.
TREOR
2004-11
Fukuda, K Moriyama, A Hashimoto, S
Crystal structure and phase transitions of strontium zirconium
diorthophosphate, SrZr(PO4)(2)
JOURNAL OF SOLID STATE CHEMISTRY 177,2004,3514-3521.
The crystal structure of SrZr(PO4)(2) at 298 K was determined from
conventional X-ray powder diffraction data using direct
methods, and it
was further refined by the Rietveld method. The structure
was triclinic
(space group P (1) over bar, Z = 2) with a = 0.77508(4)
nm, b =
0.78887(5) nm, c = 0.51251(3) nm, alpha = 95.754(3)degrees,
beta =
90.228(2)degrees, gamma = 92.474(2)degrees, and V = 0.31149(3)
nm(3).
Final reliability indices were R-wp = 8.51%, R-P = 6.07%,
and R-B =
2.46%. The powder specimens were also examined by high-temperature
XRD
and differential thermal analysis to reveal the occurrence
of phase
transitions from triclinic to monoclinic at 405 K, then
to hexagonal
(or trigonal) at 1196 K during heating. Upon cooling,
the reverse
change of the latter transition occurred at 1175 K. The
subsequent
monoclinic-to-triclinic transition was martensitic and
incomplete
during further cooling to 298 K. The monoclinic phase
is most probably
isostructural with yavapaiite. The present paper has described,
for the
first time, the higher- and lower-temperature polymorphs
of the
yavapaiite-type structure.
TREOR
2004-12
Millini, R Carluccio, LC Carati, A
Bellussi, G Perego, C Cruciani, G Zanardi,
S
ERS-12: A new layered tetramethylammonium silicate composed by
ferrierite layers
MICROPOROUS AND MESOPOROUS MATERIALS 74, 2004, 59-71.
The new layered silicate ERS-12 was synthesized using
tetraethylorthosilicate (TEOS) as source of silica and
tetramethylammonium hydroxide (TMA-OH) as a structure
directing agent.
ERS-12 crystallizes also as germanosilicate, but not as
alumino- and
titanosilicate. Structure determination of as-synthesized
ERS-12 was
performed using alpha combined approach of experimental
and molecular
modeling techniques. It is composed by a regular stacking
of ferrierite
layers, with the TMA cations located in the interlayer
region. Rietveld
refinement of the high resolution synchrotron X-ray diffraction
(SXPD)
pattern of as-synthesized ERS-12 structure was firstly
carried out in
the monoclinic P2(1)/m space group; however, to avoid
the presence of
linear Si-O-Si angles, final refinement was. performed
in the acentric
P2(1) space group, which gave unit cell parameters a =
10.5606 (2), b =
13.9692 (1), c = 7.4148(1) Angstrom, beta = 97.981(2)degrees
and
agreement factors of R-p = 8.9%, R-wp = 12.4% and R-F(2)
= 12.2%. Upon
calcination, a remarkable change of the SXPD pattern occurred
with the
contemporarily presence of sharp and asymmetrically broadened
reflections, indicative of the formation of a disordered
structure;
this was confirmed by the DIFFaX study carried out in
order to evaluate
the stacking sequences of ferrierite layers. The simulation
suggested
that the layers do not fully condense upon calcinations
to form a
completely connected framework.
TREOR
2004-13
Bulychev, BM Shpanchenko, RV Antipov, EV
Sheptyakov, DV Bushmeleva, SN Balagurov, AM
Synthesis and crystal structure of lithium beryllium deuteride Li2BeD4
INORGANIC CHEMISTRY 43, 2004, 6371-6376.
Single-phase ternary deuteride Li2BeD4 was synthesized by a
high-pressure high-temperature technique from LiD and
BeD2. The crystal
structure of Li2BeD4 was solved from X-ray and neutron
powder
diffraction data. The compound crystallizes in the monoclinic
space
group P2(1)/c with lattice parameters a = 7.06228(9) Angstrom,
b =
8.3378(1) Angstrom, c = 8.3465(1) Angstrom, beta=93.577(1)degrees,
and
Z = 8. Its structure contains isolated BeD4 tetrahedra
and Li atoms
that are located in the structure interstices. Li2BeD4
does not undergo
any structural phase transitions at temperatures down
to 8 K.
TREOR
2004-14
Hull, S Berastegui, P
Crystal structures and ionic conductivities of ternary derivatives
of
the silver and copper monohalides - II: ordered phases
within the
(AgX)(x)-(MX)(1-x) and (CuX)(x)-(MX)(1-x) (M = K, Rb and
Cs; X = Cl, Br
and I) systems
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 3156-3173.
The crystal structures of 23 ternary phases present in the systems
(AX)(x)-(MX)(1-x) (A = Ag, Cu; M= K, Rb and Cs; X= Cl,
Br and 1) have
been determined and/or refined using X-ray and neutron
diffraction
studies of powder samples. A total of 11 x = 0.333 phases
of
stoichiometry M(2)AX(3) are found (Rb2AgCl3, Cs2AgCl3,
Rb2AgBr3,
Cs2AgBr3, K2AgI3, Rb2AgI3, Cs2AgI3, K2CuCl3, K2CuBr3,
Rb2CuBr3 and
Rb2CuCl3) which crystallize in one of two closely related
crystal
structures with space group Pnma. The x = 0.4 composition
is
characterized by three compounds Cs3Cu2X5 (X= Cl, Br,
1) which all
adopt space group Pnma, whilst the x = 0.5 case comprises
the two
compounds CsAgCl2 and CsAgBr2, which possess space group
Cmcm. The
latter undergo phase transitions at 408(5) and 413(8)
K, respectively,
to higher symmetry structures in space group P4/nmm. Five
x = 0.667
compounds of stoichiometry MCu2X3 have been identified
(CsCu2Cl3,
CsCu2Br3, CsCu2I3, RbCu2Br3, and RbCu2I3). Together with
CsAg2I3, these
form a family of compounds, which crystallize in one of
two closely
related structures (space group Pbnm or Cmcm).
2004-15
Vicente, J Gil-Rubio, J Bautista, D
Sironi, A Masciocchi, N
Synthesis and reactivity of fluoro complexes: Part 2. Rhodium(I) fluoro
complexes with alkene and phosphine ligands. Synthesis
of the first
isolated rhodium(I) bifluoride complexes. Structure of
[Rh-3(mu(3)-OH)(2)(COD)(3)](HF2) by X-ray powder diffraction
INORGANIC CHEMISTRY 43, 2004, 5665-5675.
The reaction between [Rh(mu-OH)(COD)](2) (COD = 1,5-cyclooctadiene)
and
73% HF in THF gives [Rh-3(mu(3)-OH)(2)(COD)(3)](HF2) (1).
Its crystal
structure, determined by ab initio X-ray powder diffraction
methods
(from conventional laboratory data), contains complex
trimetallic
cations linked together in 1 D chains by a mu(3)-OH...
F-H-F...
HO-mu(3) sequence of strong hydrogen bonds. The complex
[Rh(mu-F)(COE)(2)](2) (COE = cyclooctene; 2), prepared
by reacting
[Rh(u-OH)(COE)(2)](2) with NEt3.3HF (3:2), has been characterized.
Complex 1 reacts with PR3 (1:3) to give [RhF(COD)(PR3)]
[R = Ph (3),
C6H4OMe-4 (4), Pr-i (5), Cy (6)] that can be prepared
directly by
reacting [Rh(U-OH)(COD)](2) with 73% HF and PR3 (1:2:2).
The reactions
of 1 with PPh3 or Et3P have been studied by NMR spectroscopy
at
different molar ratios. Complexes [RhF(PEt3)(3)] (7),
[RhF(COD)(PEt3)]
(8), and [RhF(PPh3)(3)] (9) have been detected. The complex
[Rh(F)(NBD)(Pr3P)] (NBD = norbornadiene; 10) was prepared
by the
sequential treatment of [Rh(mu-OMe)(NBD)](2) with 1 equiv
of NEt3.3HF
and Pr3P. The first isolated bifluoride rhodium(I) complexes
[Rh(FHF)(COD)(PR3)] [R = Ph (11), Pr-i (12), Cy (13)],
obtained by
reacting fluoro complexes 3, 5, and 6 with NEt3.3HF (3:1),
have been
characterized. The crystal structures of 3 and 11 have
been determined.
TREOR
2004-16
Gomez-Alcantara, MM Cabeza, A Martinez-Lara,
M Aranda, MAG
Suau, R Bhuvanesh, N Clearfield,
A
Synthesis and characterization of a new bisphosphonic acid and several
metal hybrids derivatives
INORGANIC CHEMISTRY 43, 2004, 5283-5293.
Commercial bis-(4-bromophenyl)-ether, [BrC6H4](2)-O, has been used
to
prepare 4-[4'-(diethoxyphosphoryl)phenoxy]phenyl-phosphonic
acid
diethyl ester, [(CH3CH2)(2)O3P-C6H4](2)-O, (I) following
a slight
modification of the Michaelis-Arbuzov reaction. The acid
hydrolysis of
I gave 4-(4'-phosphonophenoxy)phenyl phosphonic acid,
[H2O3P-C6H4](2)-O
(II), and both compounds have been characterized by H-1
NMR and C-13
NMR. The crystal structure of II has been determined by
single-crystal
X-ray diffraction. II crystallizes in an orthorhombic
unit cell, space
group Pbcn, with a = 7.822(3) Angstrom, b = 5.821(2) Angstrom,
c =
28.982(9) Angstrom, and V = 1319.7(7) Angstrom(3). The
final R factor
was R1 = 0.0614. The structure is layered, being held
together through
a hydrogen bonding network. II has been used as precursor
in the
syntheses of new metal (Mn, Fe, Co, Ni, Cu, and Zn) bisphosphonates.
The syntheses were carried out using a fixed metal/bisphosphonic
acid
molar ratio of 2.1:1 and the influence of the pH in the
reactions has
been studied. Nine new compounds have been isolated:
Mn-2(O3PC6H4OC6H4PO3)(.)1.5H(2)O (III),
Mn-5(OH)(2)(O3PC6H4OC6H4PO3)(2)(.)2H(2)O (IV),
Fe(HO3PC6H4OC6H4PO3)(.)0.5H(2)O M, CO2(O3PC6H4OC6H4PO3)(.)2H(2)O
(VI),
Ni-2(O3PC6H4OC6H4PO3)(.)3H(2)O (VII), Ni-2(O3PC6H4OC6H4PO3)(.)2H(2)O
(VIII), Cu-2(O3PC6H4OC6H4PO3) (IX), Zn-2(O3PC6H4OC6H4PO3)
(X), and
Zn(HO3PC6H4OC6H4PO3H) (XI). Compound IX crystallizes in
an orthorhombic
unit cell, space group Pbcn, and unit cell parameters
a = 8.1012(5)
Angstrom, b = 5.3109(3) Angstrom, c = 29.2595(5) Angstrom,
and V =
1258.8(1) Angstrom(3). Its structure has been solved by
ab initio
powder diffraction and refined by the Rietveld method
to R-F = 0.042.
IX has a pillared layer framework with highly distorted
CuO5 groups
sharing edges to give isolated dimers. XI was indexed
in a monoclinic
unit cell, space group P112(1), with parameters a = 9.4991
(9)
Angstrom, b = 5.0445(5) Angstrom, c = 29.131(2) Angstrom,
gamma =
91.945(7)degrees, and V = 1395.1(3) Angstrom(3). Its structure
has been
refined by the Rietveld method, R-F = 0.054, since it
is isostructural
with the known compound, Zn[HO3P(C6H4)(2)PO3H]. All solids
were also
characterized by thermal analysis and IR and UV-Vis spectroscopies.
TREOR
2004-17
Chernaya, VV Tsirlin, AA Shpanchenko, RV
Antipov, EV Gippius, AA
Morozova, EN Dyakov, V Hadermann,
J Kaul, EE Geibel, C
Crystal structure and properties of Na2MVO(PO4)(2), the new
vanadyl(IV)phosphates M=Ca and Sr
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 2875-2880.
Two new complex vanadyl(IV)phosphates Na2MVO(PO4)(2) (M = Ca, Sr) were
synthesized in evacuated quartz ampoules and investigated
by means of
X-ray diffraction, electron microscopy, DTA, ESR and magnetic
susceptibility measurements. The crystal structure of
Na2SrVO(PO4)(2)
was solved ab initio from X-ray powder diffraction data.
Both compounds
are isostructural: a = 10.5233(3) Angstrom, b = 6.5578(2)
Angstrom, c =
10.0536(3) Angstrom and a = 10.6476(3) Angstrom, b = 6.6224(2)
Angstrom, c = 10.2537(3) Angstrom for Ca and Sr, respectively;
S.G.
Pnma, Z = 4. The compounds have a three-dimensional structure
consisting of V4+ O-6 octahedra connected by PO4 tetrahedra
via five of
the six vertexes forming a framework with cross-like channels.
The
strontium and sodium atoms are located in the channels
in an ordered
manner. Electron diffraction as well as high-resolution
electron
microscopy confirmed the structure solution. The new vanadylphosphates
are Curie-Weiss paramagnets in a wide temperature range
down to 2 K
with theta = 12 and 5 K for Ca and Sr phases, respectively.
TREOR
2004-18
Albov, DV Davydov, DV Chernyshev, VV
Di-mu-hydroxo-bis[(N,N,N ',N '-tetramethylethylenediamine)copper(II)]
dichloride from X-ray powder data
ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE 60, 2004,
M1193-M1195.
The crystal structure of the title complex,
[Cu-2(OH)(2)-(TMEDA)(2)]Cl-2 (TMEDA is
N,N,N',N'-tetramethylethylene-diamine, C6H16N2) has been
characterized
by X-ray powder diffraction. The cation is a binuclear
complex with a
Cu...Cu distance of 3.031 (7) Angstrom and occupies a
special position
of 222 symmetry, while the chloride anions are on a twofold
axis. There
is a hydrogen bond linking a bridging hydroxy group with
the anion
[O...Cl = 2.993 (14) Angstrom].
TREOR
2004-19
Filonenko, VP Sundberg, M Werner, PE
Zibrov, IP
Structure of a high-pressure phase of vanadium pentoxide beta-V2O5
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 60, 2004, 375-381.
A high-pressure phase of vanadium pentoxide, denoted beta-V2O5, has
been prepared at P = 6.0 GPa and T = 1073 K. The crystal
structure of
beta-V2O5 has been studied by X-ray and neutron powder
diffraction, and
high-resolution transmission electron microscopy. The
V atoms are
six-coordinated within distorted VO6 octahedra. The structure
is built
up of quadruple units of edge-sharing VO6 octahedra linked
by sharing
edges along [ 010] and mutually connected by sharing corners
along
[001]. This arrangement forms layers of V4O10 composition
in planes
parallel to ( 100). The layers are mutually held together
by weak
forces. beta-V2O5 is metastable and transforms to alpha-V2O5
at 643 -
653 K under ambient pressure. Structural relationships
between beta-
and alpha-V2O5, and between beta-V2O5 and B-Ta2O5-type
structures are
discussed. The high-pressure beta-V2O5 layer structure
can be
considered as the parent of a new series of vanadium oxide
bronzes with
cations intercalated between the layers.
TREOR
2004-20
Platteau, C Lefebvre, J Affouard, F
Derollez, P
Ab initio structure determination of the hygroscopic anhydrous form
of
a-lactose by powder X-ray diffraction
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 60, 2004, 453-460.
Annealing of alpha-lactose monohydrate at 408 K yielded a mixture of
this compound with hygroscopic anhydrous alpha-lactose.
A powder X-ray
diffraction pattern of this mixture was recorded at room
temperature.
The starting structural model of hygroscopic alpha-lactose
was found by
a Monte Carlo simulated-annealing method. The final structure
was
obtained through Rietveld refinements, with soft restraints
on
interatomic bond lengths and bond angles, and crystalline
energy
minimization to locate the H atoms of the hydroxy groups.
The
crystalline cohesion is achieved by networks of O - H
... O hydrogen
bonds that differ from those of the monohydrate phase.
The width of the
Bragg peaks is interpreted by a phenomenological microstructural
approach in terms of isotropic size effects and anisotropic
strain
effects.
TREOR
2004-21
Rosdahl, J Persson, I Lars, K Stahl,
K
On the solvation of the mercury(I) ion. A structural, vibration
spectroscopic and quantum chemical study
INORGANICA CHIMICA ACTA 357, 2004, 2624-2634.
The structure of solid
anhydrous mercury(l) trifluoromethanesulfonate, Hg-2(CF3SO3)(2)
(1),
has been determined by powder diffraction methods. The
structure
comprises of discrete molecules, where each mercury binds
to an oxygen
atom in the anion, forming an almost linear O-Hg-Hg-O
entity; the
Hg-Hg-O angle is 173degrees and the Hg-Hg and Hg-O bond
lengths are
2.486(6) and 2.099(22) Angstrom, respectively.
TREOR
2004-22
Kyoi, D Sato, T Ronnebro, E Tsuji,
Y Kitamura, N Ueda, A
Ito, M Katsuyama, S Hara, S
Noreus, D Sakai, T
A novel magnesium-vanadium hydride synthesized by a
gigapascal-high-pressure technique
JOURNAL OF ALLOYS AND COMPOUNDS 375, 2004, 253-258.
A magnesium-based vanadium-doped hydride was prepared in a
high-pressure anvil cell by reacting a MgH2-25%V molar
mixture at 8 GPa
and 873 K. The new magnesium-vanadium hydride has a cubic
F-centred
substructure (a = 4.721 (1) Angstrom), with an additional
superstructure, which could be described by a doubling
of the cubic
cell axis and a magnesium atom framework, including an
ordered
arrangement of both vanadium atoms and vacancies (a =
9.437(3)
Angstrom, space group Fm (3) over barm (no. 225), Z =
4, V =
840.55,Angstrom(3)). The metal atom structure is related
to the Ca7Ge
type structure but the refined metal atom composition
with vacancies on
one of the magnesium sites corresponding to Mg6V nearly
in line with
EDX analysis.
TREOR
2004-23
Song, GB Han, CQ Chen, XL Liang,
JK Liu, QL Zhou, YQ Liu, FS
Rao, GH
Subsolidus phase relations and crystal structure of compounds in the
PrOx-CaO-CuO system
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 2394-2404.
The subsolidus phase relations of the PrOx-CaO-CuO pseudo-ternary
system sintered at 950-1000degreesC have been investigated
by X-ray
powder diffraction. In this system, there exist one compound
Ca10Pr4Cu24O41, one Ca2Pr2Cu5O10-bascd solid solution,
seven
three-phase regions and two two-phase regions. The crystal
structures
of Ca10Pr4Cu24O41, and Ca2Pr2Cu5O10-based solid solution
have been
determined. Compound Ca10Pr4Cu24O41 crystallizes in an
orthorhombic
cell with space group D-2h(20) - Cccm, Z = 4. Its lattice
parameters
are a = 11.278(2) Angstrom, b = 12.448(3) Angstrom and
c = 27.486(8)
Angstrom. The crystal structure of Ca2Pr2Cu5O10-based
solid solution is
an incommensurate phase based on the orthorhombic NaCuO2
type subcell.
The lattice parameters of the subcell of the Ca2.4Pr1.6Cu5O10
are a(0)
= 2.8246(7) Angstrom, b(0) = 6.3693(5) Angstrom, c(0)
= 10.679(1)
Angstrom, and those of the orthorhombic superstructure
are with a =
5a(0), b = b(0), c = 5c(0). The Ca2.4Pr1.6Cu5O10 structure
can also be
determined by using a monoclinic supercell with space
group C-2h(5) -
P2(1)/c, Z = 4, a = 5a(0), b = b(0), c = c(0)/sin beta
and beta =
104.79(1)degrees or 136.60(1)degrees, V = 5a(0)b(0)c(0).
TREOR
2004-24
Bellitto, C Bauer, EM Righini, G
Altomare, A
Synthesis and magnetic properties of a new Cr(II)
ammonium-ethyl-phosphonate: Cr-1.5[H3N(CH2)(2)PO3](SO4)
.
2H(2)O
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 272-76, 2004, 1060-1061.
A new molecule based magnet of formula Cr-1.5[H3N(CH2)(2)PO3](SO4)
(.)
2H(2)O has been prepared and characterized. The magnetization
vs. field
and temperature measurements revealed the compound to
be a soft
weak-ferromagnet at T-N = 4.9 K.
TREOR
2004-25
Botez, CE Stephens, PW Omotoso, O
Crystal structure of dicalclum chromate hydrate
POWDER DIFFRACTION 19, 2004, 133-136.
Direct methods and Rietveld analysis were applied to high-resolution
synchrotron X-ray powder diffraction data to solve the
crystal
structure of dicalcium chromate hydrate (Ca2CrO5.3H(2)O).
The compound
crystallizes in monoclinic symmetry (space group Cm, Z=2),
with a
=8.23575(5) Angstrom, b=7.90302(4) Angstrom, c=5.20331(3)
Angstrom, and
beta=98.0137(3)degrees. The structure is built from double-layers
of
CrO4 tetrahedra and CaO8 polyhedra that run parallel to
the (001)
plane.
TREOR, DICVOL
2004-26
Ivashkevich, LS Lyakhov, AS Selevich, AF
Lesnikovich, AI
Crystal structure determination of Ga-3(H3O)H-8(PO4)(6) . 6 H2O
from X-ray powder diffraction data
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 219, 2004, 267-271
The crystal structure of the gallium hydrogen phosphate hydrate,
Ga-3(H3O)H-8(PO4)(6) (.) 6 H2O, has been determined from
X-ray powder
diffraction data. The structure is trigonal, space group
P31c (No.
159), with unit cell dimensions a = 9.0227(1) Angstrom,
c = 16.6389(3)
Angstrom, V = 1173.08(3) Angstrom(3), Z=2, and D-x = 2.59g/cm(3).
The
structure was solved by direct methods using EXPO program
and refined
by FULLPROF package to R-Bragg value of 8.6%. Positions
of hydrogen
atoms were not defined. There are three unique gallium
atoms in the
crystal structure, having octahedral oxygen coordination.
GaO6
octahedra are linked together via the corners Of PO4 tetrahedra
to form
a three-dimensional network with channels running along
the c axis.
There are two types of water molecules in the crystal,
which
essentially differ in their atomic environment. Oxonium
cations, lying
on crystallographic threefold axis, are surrounded by
oxygen atoms of
the phosphate groups and water molecules.
TREOR
2004-27
Thoma, SG Bonhomme, F Cygan, RT
Synthesis, crystal structure, and molecular modeling of a layered
manganese(II) phosphate: Mn-3(PO4)(4) . 2(H3NCH2CH2)(3)N
center
dot 6(H2O)
CHEMISTRY OF MATERIALS 16, 2004, 2068-2075.
A novel layered manganese(II) phosphate,
Mn-3(PO4)(4).2(H3NCH2CH2)(3)N.6(H2O), has been synthesized
solvothermally using tris(2-aminoethyl)amine (TREN) as
a template. The
structure was solved A initio using X-ray powder diffraction
data and
confirmed by molecular modeling.
The compound crystallizes in the trigonal space group
P $(3)
over bar $ c1 with a = 8.8706(4) Angstrom, c = 26.158(2)
Angstrom, and
V= 1782.6(2) Angstrom(3). The structure consists of layers
of corner
sharing Mn(II)O-4 and PO4 tetrahedra forming infinite
[Mn-3(PO4)(4)](6-)macroanions with 4.6 net topology, sandwiched
by
layers of TREN and water molecules. The protonated TREN
molecules
provide charge balancing for the inorganic sheets; the
interlayer
stability is accomplished mainly by a network of hydrogen
bonds between
water molecules and the inorganic macroanions. This hybrid
organic/inorganic layered material can be reversibly dehydrated.
TREOR
2004-28
Rukiah, M Lefebvre, J Descamps, M
Hemon, S Dzyabchenko, A
Ab initio structure determination of m-toluidine by powder X-ray
diffraction
JOURNAL OF APPLIED CRYSTALLOGRAPHY 37, 2004, 464-471.
The powder X-ray diffraction pattern of the crystalline phase of
m-toluidine has been recorded with a sensitive curved
detector (CPS120)
at 150 K. The structure has been solved by real-space
methods (
simulated annealing) followed by Rietveld refinements
with phenyl rings
as rigid bodies and with soft constraints on bond lengths
for
peripheral atoms. The cell is monoclinic with space group
P2(1)/c and Z
= 8. Equivalent molecules form chains along c. The crystalline
cohesion
is achieved by N-H...N hydrogen bonds between neighbouring
chains of
non-equivalent molecules and by van der Waals interactions
of
neighbouring chains of equivalent molecules. The hydrogen-bonding
network has been confirmed by lattice-energy minimization.
Anisotropic
strain effects of the cell have been calculated. The directions
of the
minimal strains correspond to the directions of the hydrogen
bonds. An
explanation of the difficulty to crystallize the metastable
phase is
given.
TREOR, N-TREOR
2004-29
Vila, E Rojo, JM Iglesias, JE Castro,
A
Polymorphism and electrical properties in the new oxide Bi6Mo2O15
CHEMISTRY OF MATERIALS 16, 2004, 1732-1739.
A new oxide of composition Bi6Mo2O15 has been isolated in the binary
system Bi2O3- MoO3. A wet-chemistry procedure, different
from
coprecipitation, has been used to prepare a nanosized,
very reactive
precursor. Annealing at different temperatures and for
different time
lengths leads to isolated polycrystalline polymorphs.
X-ray powder
diffraction studies on the hitherto unknown low-temperature
form,
L-Bi6Mo2O15, show that it crystallizes in the monoclinic
system, with
unit-cell parameters a = 29.0674(5) Angstrom, b = 5.64795(7)
A, c
8.6620(1) Angstrom, beta = 97.979(1)degrees, and V = 1408.3
Angstrom(3). The high-temperature polymorph, H-Bi6Mo2O15,
belongs to
the well-known [Bi12O14] columnar structural type. The
relationship
between the unit-cell parameters of both phases points
at the
connection of their structural frameworks. Impedance spectroscopy
measurements show that the transition L-H-Bi6Mo2O15 is
partially
reversible, as well as the existence of a second high-temperature
phase
H', similar to H. In contrast, the transition H-->H'-Bi6Mo2O15
is not
reversible. These materials turn out to be good ionic
conductors, with
conductivities in the order L < H < H' for all temperatures
tested.
2004-30
Pan, ZG Cheung, EY Harris, KDM Constable,
EC Housecroft, CE
Structural aspects of a dendrimer precursor determined directly from
powder X-ray diffraction data
CRYSTAL GROWTH & DESIGN 4, 2004, 451-455.
The structure of 3,5-dimethoxybenzyl alcohol has been determined
directly from powder X-ray diffraction data using the
genetic algorithm
technique for structure solution followed by Rietveld
refinement. This
material is the precursor to a family of dendrimer materials,
and
structural features exhibited by 3,5-dimethoxybenzyl alcohol
in the
solid state may be important in the rationalization of
higher
generation dendrimer materials within this family.
TREOR, DICVOL
2004-31
Ronnebro, E Kyoi, D Blomqvist, H
Noreus, D Sakai, T
Structural characterization of Mg3CrH similar to 6 - a new
high-pressure phase synthesized in a multi-anvil cell
at 8 GPa
JOURNAL OF ALLOYS AND COMPOUNDS 368, 2004, 279-282.
With modem X-ray diffraction refinement methods it was possible to
identify the first phase in the Mg-Cr-H system, Mg3CrH-6
from minute
sample volume in spite of poor crystallinity and coexisting
impurity
phases. The new hydride was synthesized at 8 GPa in a
high-pressure
multi-anvil cell at 873 K. An orthorhombic unit cell was
found with a =
9.635(2) Angstrom, b = 8.615(2) Angstrom, c = 4.8040(7)
Angstrom, space
group Pnam (no. 62) Z = 4. V = 398.77 Angstrom(3). Chromium
is
surrounded by a distorted cube of magnesium atoms with
average Cr-Mg
distances of 2.9(1) Angstrom. The hydrogen positions were
not possible
to determine, as only a small sample amount could be prepared.
If the
metal atom structure is compared to already known metal
hydrides it can
be concluded that Mg3CrH-6 consists of chromium hydrido
complexes
counterbalanced by magnesium ions. A high hydrogen content
was
confirmed with thermal desorption spectroscopy.
TREOR
2004-32
Loiseau, T Serre, C Huguenard, C
Fink, G Taulelle, F Henry, M
Bataille, T Ferey, G
A rationale for the large breathing of the porous aluminum
terephthalate (MIL-53) upon hydration
CHEMISTRY-A EUROPEAN JOURNAL 10, 2004, 1373-1382.
Aluminum 1,4-benzenedicarboxylate
Al(OH)[O2C-C6H4-CO2](.)[HO2C-C6H4-CO2H](0.70) or MIL-53
as (Al) has
been hydrothermally synthesized by heating a mixture of
aluminum
nitrate, 1,4-benzenedicarboxylic acid, and water, for
three days at
220degreesC. Its 3D framework is built up of infinite
trans chains of
corner-sharing AlO4(OH)(2) octahedra. The chains are interconnected
by
the 1,4-benzenedicarboxylate groups, creating ID rhombic-shaped
tunnels. Disordered 1,4-benzenedicarboxylic acid molecules
are trapped
inside these tunnels. Their evacuation upon heating, between
275 and
420degreesC. leads to a nanoporous open-framework (MIL-53ht
(Al) or
Al(OH)[O2C-C6H4-CO2]) with empty pores of diameter 8.5
Angstrom. This
solid exhibits a Langmuir surface area of 1590(1) m(2)g(-1)
together
with a remarkable thermal stability, since it starts to
decompose only
at 500degreesC. At room temperature, the solid reversibly
absorbs water
in its tunnels, causing a very large breathing effect
and shrinkage of
the pores. Analysis of the hydration process by solid-state
NMR (H-1,
C-13, Al-27) has clearly indicated that the trapped water
molecules
interact with the carboxylate groups through hydrogen
bonds, but do not
affect the hydroxyl species bridging the aluminum atoms.
ne hydrogen
bonds between water and the oxygen atoms of the framework
are
responsible for the contraction of the rhombic channels.
The structures
of the three forms have been determined by means of powder
X-ray
diffraction analysis. Crystal data for MIL-53 as (Al)
are as follows:
orthorhombic system, Pnma (no. 62), a 17.129(2), b = 6.628(1),
c =
12.182(1) A; for MIL-53ht (Al), orthorhombic system, Imma
(no. 74), a =
6.608(1), b = 16.675(3), c = 12.813(2) Angstrom; for MIL-53
lt (Al),
monoclinic system, Cc (no. 9), a = 19.513(2), b = 7.612(1),
c =
6.576(1) Angstrom, beta = 104.24(1)degrees.
TREOR
2004-33
Ferreira, A Lin, Z Soares, MR Rocha,
J
Synthesis and ab initio structure determination from powder diffraction
data of K4Sn2Si6O18
EUROPEAN POWDER DIFFRACTION EPDIC 8, MATERIALS SCIENCE FORUM, 443-4,
2004, 329-332.
The crystal structure of a new potassium stannosilicate K4Sn2Si6O18
(AV-11) has been determined ab initio from powder X-ray
diffraction
data. The unit cell is trigonal, space group R3 (no. 146),
Z=3 with
cell dimensions a = 10.1587, c = 14.8039 Angstrom, gamma=
120degrees, V
= 1323 Angstrom(3). The structure is made up of SnO6 octahedra
and SiO4
tetrahedra by sharing comers. The SiO4 tetrahedra form
a helix chain,
periodically repeating every six tetrahedra. These chains
extend along
the [001] direction and are linked by isolated Sn-O octahedron
giving a
mixed framework.
TREOR
2004-34
Scordari, F Ventruti, G Gualtieri, AF
The structure of metahohmannite, Fe-2(3+)[O(SO4)(2)] . 4H(2)O,
by in situ synchrotron powder diffraction
AMERICAN MINERALOGIST 89, 2004, 365-370.
Metahohmannite, Fe-2(3+)[O(SO4)(2)].4H(2)O, is a hydrated sulfate of
ferric iron that occurs in sulfate deposits in the desert
areas of
Northern Chile. The compound used for this study was obtained
as a
dehydration product of hohmannite, Fe-2(3+)[O(SO4)(2)].(4+4)H2O.
Intensities for the structure analysis were collected
from a powdered
sample using in situ synchrotron X-ray powder diffraction
at ESRF
(Grenoble, France). The structure was solved ab initio
by profile
deconvolution and the application of standard Patterson
and difference
Fourier maps. The structure was refined to R-p = 5.46%
using the
Rietveld method. Metahohmannite crystallizes in the triclinic
system,
space group P (1) over bar with unit-cell parameters a
= 7.3484(5)
Angstrom, b = 9.7710(6) Angstrom, c = 7.1521(5) Angstrom,
alpha =
91.684(5)degrees, beta = 98.523 (5), gamma = 86.390(5)degrees,
and Z =
2. The structure consists of four Fe3+ octahedra and four
sulfate
tetrahedra, which share vertices and edges to form a complex
building
block of Fe-4(3+)[O-2(SO4)(4)].8H(2)O composition. Such
blocks are
connected to form chains running parallel to the c axis.
A complicated
system of hydrogen bonds connects adjacent chains into
a
three-dimensional network. Finally, the crystal structures
of
metahohmannite, hohmannite, and amarantite are compared
and the
geometrical features discussed in detail.
TREOR
2004-35
Muhle, C Dinnebier, RE van Wullen, L
Schwering, G Jansen, M
New insights into the structural and dynamical features of lithium
hexaoxometalates Li7MO6 (M= Nb, Ta, Sb, Bi)
INORGANIC CHEMISTRY 43, 2004, 874-881.
We present a (re)investigation of the hexaoxometalates Li8MO6 (M =
Sn,
Pb, Zr, Hf) and Li7MO6 (M = Nb, Ta, Sb, Bi). Lithium motion
and ionic
conductivity in the hexaoxometalates were studied using
impedance
spectroscopy (for Li7MO6, M = Sb, Bi, Ta) and Li-6 and
Li-7 solid-state
nuclear magnetic resonance (for Li7TaO6). The NMR data
indicate a
considerable exchange of Li among the tetrahedral and
octahedral voids
even at ambient temperature. In an investigation of the
crystal
structures using laboratory and synchrotron X-ray powder
diffraction
techniques, the structures of Li7TaO6, Li7NbO6, and Li7SbO6
could be
solved and refined. All three reveal a triclinic metric
(Li7SbO6,
triclinic, P (1) over bar, a = 5.38503(6) Angstrom, b
= 5.89164(7)
Angstrom, c = 5.43074(6) Angstrom, alpha = 117.2210(6)degrees,
beta =
119.6311(6)0, gamma = 63.2520(7)degrees, V = 127.454(3)
Angstrom(3), Z
= 1; Li7NbO6, triclinic, P (1) over bar, a = 5.37932(9)
Angstrom, b =
5.91942(11) Angstrom, c = 5.37922(9) Angstrom, alpha =
117.0033(9)-,
beta = 119.6023(7)degrees, gamma = 63.2570(9)degrees,
V = 126.938(4)
Angstrom(3), Z = 1; Li7TaO6, triclinic, P (1) over bar,
a = 5.38486(2)
Angstrom, b = 5.92014(3) Angstrom, c = 5.38551(2) Angstrom,
alpha =
117.0108(2)degrees, beta = 119.6132(2)degrees, gamma =
63,2492(2)degrees, V = 127.208(1) Angstrom(3), Z = 1.
TREOR
2004-36
Bakhmutova-Albert, EV Bestaoui, N Bakhmutov,
VI Clearfield, A Rodriguez, AV Llavona,
R
A novel cadmium aminophosphonate: X-ray powder diffraction structure,
solid-state IR and NMR spectroscopic determination of
the fine
structure of the organic moieties
INORGANIC CHEMISTRY 43, 2004, 1264-1272.
A new divalent cadmium phosphonate, Cd2Cl2(H2O)(4)(H2L), has been
synthesized from the ethylenediamine-N,N'-bis(methylenephosphonic
acid)
(H4L). The obtained microcrystalline compound has been
characterized by
solid-state IR spectra and C-13, P-31, and Cd-113 CP MAS
NMR. The
static P-13 NMR spectra have been also recorded to give
the delta(11),
delta(22), and delta(33) chemical shift parameters for
both compounds.
The spectral data, collected for Cd2Cl2-(H2O)(4)(H2L),
are in an
agreement with its X-ray powder diffraction structure
solved with the
cell dimensions a = 16.6105(10), b = 7.1572(4), and c
= 6.8171(4)
Angstrom and beta = 98.327(4)degrees. The octahedral coordination
sphere of the cadmium atoms consists of two phosphonate
oxygen atoms,
two water oxygen atoms, and the two chlorine atoms. Cadmium
atoms are
bridged by the chlorine atoms forming four-membered rings.
The
phosphorus atoms exhibit a tetrahedral coordination with
two oxygen
atoms bonded to the cadmium atoms with P-O distances of
1.503(10) and
1.504(10) Angstrom. The third oxygen atom, showing a longer
P-O
distance (1.546(9) Angstrom), is not bonded to the metal
center, nor is
it bonded to a proton. The combined IR and NMR proton-phosphorus
cross-polarization kinetic data together with the X-ray
data confirm
that the cadmium phosphonate has the zwitterionic structure
(NH2+CH2P(O2Cd2)O-) similar to the initial aminophosphonic
acid H4L.
TREOR
2004-37
Barea, E Navarro, JAR Salas, JM
Masclocchi, N Galli, S Sironi, A
Coordination frameworks containing the pyrimidin-4-olate ligand.
Synthesis, thermal, magnetic, and ab initio XRPD structural
characterization of nickel and zinc derivatives
INORGANIC CHEMISTRY 43, 2004, 473-481.
Extended coordination frameworks containing the pyrimidin-4-olate
ligand (4-pymo) and Zn(II) and Ni(II) metal ions have
been obtained by
solid state reactions and have been fully characterized
by
spectroscopic, thermal, and magnetic measurements and
by ab initio
XRPD. The reaction of ZnO and 4-Hpymo at 140 degreesC
gives a solid
microcrystalline phase, Zn(4-PYMO)(2) (1). Its 3D framework
contains
Zn(II) centers linked by 4-pymo ligands acting in two
different
coordination modes, namely, the N,N'- and the N,O-exo-bidentate
ones,
which result in a pseuclotetrahedral ZnN3O chromophore.
Thermal
treatment of the "molecular' Ni(4-pymo)(2)(H2O)(4) complex
(2) above
140 degreesC gives an anhydrous amorphous material analyzing
as
Ni(4-PYMO)(2) (3a). Further heating of this material above
388 degreesC
results in the formation of the microcrystalline layered
Ni(4-PYMO)(2)
species (3b), in which Ni(II) centers are bridged by N,O-exo-bidentate
4-pymo ligands (assisted by longer Ni...N contacts). The
thermal
dependence of the magnetic susceptibility has been studied
for the
paramagnetic species 2 and 3a. 2 shows a weak antiferromagnetic
interaction [J = -0.313(5) cm(-1)] transmitted through
the multiple
H-bonding interactions between the exocyclic pyrimidine
and water
oxygen atoms coordinated to the metal centers. 3a behaves
as a 2D
Heisenberg antiferromagnet with J = -4.11(3) cm(-1).
TREOR
2004-38
Vanhoyland, G Le Bail, A Mullens, J
Van Poucke, LC
Characterization and structure determination of ammonium bismuth
oxalate hydrate, Bi(NH4)(C2O4)(2) . xH(2)O
INORGANIC CHEMISTRY 43, 2004, 785-789.
From on-line coupled TGA-MS and TGA-FTIR measurements, in combination
with a quantitative chemical analysis, it was deduced
that the chemical
formula for an unknown bismuth oxalate compound had to
be
Bi(NH4)(C2O4)(2).3.71(6)H2O. Solution of the crystallographic
structure
on the basis of X-ray powder data proved this formula
to be correct.
The diffraction pattern was indexed by a tetragonal unit
cell [a and c
respectively 11.6896(2) and 9.2357(3) Angstrom; M-20 =
195 and F-30 =
302; Z(calc) = 4], from which the space group /4(1)/amd
(No. 141) was
derived. Direct methods were applied to solve the structure.
The
initial structural model was subsequently refined by means
of the
Rietveld method (R-B = 8.0%, R-wP = 14.0%). Bi is 8-fold
coordinated by
oxygen from the oxalate anions. Since these BiO8 polyhedrons
do not
share any edges or vertexes, an open framework is formed
with water and
ammonium molecules between. As a result, water can easily
be removed,
which is clearly indicated by the instant weight loss
in the TGA upon
heating. Moreover, as shown by HT-XRD, this process of
water exchange
is reversible as long as the heating temperature does
not exceed 100
degreesC.
TREOR, DICVOL
2004-39
Serda, P Grochowski, J Duddeck, H
The structure of marmesinin by powder and single-crystal diffraction
methods
JOURNAL OF ALLOYS AND COMPOUNDS 362, 2004, 224-230.
The crystal and molecular structure of marmesinin C20H24O9, a
furocoumarine beta-D-glucoside, an important biocontrolling
compound
isolated from the fruits of Ammi majus L. was determined
from
high-resolution powder diffraction using simulated annealing
and,
independently, from microcrystal diffraction. Both structural
models
were in good agreement. High-resolution powder diffraction
patterns
recorded with synchrotron radiation proved to be an efficient
method
for crystal structure determination of poorly-crystallizing
natural
products. (C) 2003 Elsevier B.V. All rights reserved.
TREOR
2004-40
Neels, A Wang, Y Stoeckli-Evans, H
TStudying the structure of metal-organic polymers using in-house powder
X-ray diffraction data: structural transformations induced
by thermal
treatment
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 219, 2004, 892-901.
The use of X-ray powder diffraction for the structure determination
of
inorganic, organic and metal-organic compounds has grown
impressively
over the last ten years. In supramolecular chemistry,
the knowledge of
the three-dimensional structure of a material is essential
for the
discussion of its macroscopic behaviour, and as a result
the design of
new functionalized materials.
The ab initio crystal structure determination of previously
unknown
metal-organic compounds is still rare but is a field of
high interest
and activity. Here we describe the formation of ID coordination
polymers and the phase transformation processes that lead
to the
formation of 3D polymers on heating, accompanied by colour
changes.
The reaction of pyrazine-2,5-dimethyl-3,6-dicarboxylic
acid with first
row transition metal salts lead to the formation of coordination
polymers always in the form of microcrystalline powders.
With manganese
and nickel salts isostructural 1D coordination polymers
were obtained.
With zinc chloride and copper chloride isomorphous ID
coordination
polymers were obtained. The thermal decomposition of the
nickel and
copper polymers were studied and it was shown that on
the loss of the
coordinated water molecules new 3D coordination polymers
could be
obtained. In both the ID and 3D coordination polymers
the metal atoms
have octahedral geometry in N2O4 environments. The crystal
structures
of all six complexes have been determined from powder
X-ray diffraction
data. Crystal data: (1) crystal symmetry monoclinic [space
group
P2(1)/c, a = 7.4645(1), b = 8.9472(2), c = 7.6166(1) Angstrom,
beta =
92.198(2)degrees]; (2) crystal symmetry orthorhombic [space
group Pbcn,
a = 7.4060(2), b = 7.1857(2), c = 9.0661(2) Angstrom];
(3) crystal
symmetry monoclinic [space group P2(1)/c, a = 6.9376(9),
b =
7.1306(12), c 8.5852(20) Angstrom, beta = 113.299(18)degrees];
(4)
crystal symmetry orthorhombic [space group Pbcn, a = 9.0593(2),
b
7.4410(1), c = 14.6697(2) Angstrom]; (5) crystal symmetry
orthorhombic
[space group Pbcn, a = 8.9727(1), b = 7.2354(1), c = 15.0444(2)
Angstrom]; (6) crystal symmetry monoclinic [space group
P2(1)/c, a =
6.9133(4), b = 7.9927(6), c = 8.2084(6)Angstrom, beta
=
110.066(6)degrees].
N-TREOR
2004-41
Cordier, S Roisnel, T Poulain, M
TSynthesis and characterization of the novel Nb3O5F5 niobium
oxyfluoride: the term n=3 of the NbnO(2n-1)F(n+2) series
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 3119-3126.
The solid-state synthesis of the oxyfluoride Nb3O5F5, its crystal
structure determined from X-ray powder diffraction data
as well as some
physical characterizations, are reported. Nb3O5F5 constitutes
the term
n = 3 of the NbnO2n-1Fn+2 series related to the Dion-Jacobson
phases.
It crystallizes, at room temperature, in the tetragonal
system (space
group I4/mmm (no. 139); Z = 4; a = 3.9135(1) Angstrom,
c = 24.2111(2)
Angstrom, and V = 370.80(Angstrom(3)) The crystal structure
appears to
be an in-between of the three-dimensional network of NbO2F
and the
two-dimensional packing of NbOF3 (term n = 1 of the NbnO2n-1Fn+2
series). This layered structure consists of slabs made
of three
Nb(O2F)(6) corner-linked octahedra in thickness (n = 3)
shifted one
from another by a (1/2a + 1/2b)/transiation. Oxygen and
fluorine atoms
are randomly distributed over all the ligand sites.
N-TREOR, DICVOL
2004-42
Rukiah, M Lefebvre, J Hernandez, O
van Beek, W Serpellon, M
Ab initio structure determination of the Gamma form of D-sorbitol
(D-glucitol) by powder synchrotron X-ray diffraction
JOURNAL OF APPLIED CRYSTALLOGRAPHY 37, 2004, 766-772.
A high-resolution powder synchrotron X-ray diffraction pattern of the.
form of D-sorbitol has been recorded at 293 K on the BM1B
beamline at
the ESRF ( Grenoble). The starting model of the structure
was found by
Monte Carlo simulated annealing. The final structure was
obtained
through Rietveld refinements performed with soft restraints
on
interatomic bond lengths and angles. The symmetry is orthorhombic,
space group P2(1)2(1)2, with 12 molecules within the cell
[a = 24.3012
( 2), b = 20.5726 ( 2), c = 4.8672 ( 1) Angstrom, V =
2433.30 ( 3)
Angstrom(3), Z' = 3, 36 non-H independent atoms]. Crystalline
cohesion
between neighbouring molecules is achieved by three networks
of O-H...O
hydrogen bonds. The width of the Bragg peaks is interpreted
through a
microstructural approach in terms of anisotropic strain
effects.
N-TREOR
2004-43
Yang, QB Wang, PL Li, YX Yin, QR
Werner, PE Moliterni, AGG Cheng, YB
On the superstructure of KTiO2(OH)
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 219, 2004, 227-230.
The superstructure of potassium titanate, KTiO2(OH), prepared by
hydrothermal synthesis has been determined from synchrotron
powder
diffraction data. It is shown that the unit cell of the
superstructure
is rhombohedral: a = 11.13848 Angstrom, alpha = 52.7336degrees.
The
structure has been determined and refined in space group
R (3) over
barc to R-F = 0.074. The distribution of hydrogen atoms
as hydroxy
groups can be explained from the crystal structure described
by the
supercell.
N-TREOR
2004-44
Mahe, N Bataille, T
Synthesis, crystal structure from single-crystal and powder x-ray
diffraction data, and thermal behavior of mixed potassium
lanthanide
squarates: Thermal transformations of layered
[Ln(H2O)(6)]K(H2C4O4)(C4O4)(2) into pillared LnK(C4O4)2
(Ln = Y, La,
Gd, Er)
INORGANIC CHEMISTRY 43, 2004, 8379-8386.
A new series of mixed potassium and rare-earth squarates,
[Ln(H2O)(6)]K(H2C4O4)(C4O4)(2) (Ln = Y, La, Gd, Er), has
been
synthesized and structurally characterized from single-crystal
X-ray
diffraction and spectroscopic analyses. The yttrium-based
compound
crystallizes with a monoclinic symmetry, space group C2/c
[a =
8.3341(2) Angstrom, b = 37.7094(g) Angstrom, c = 11.7195(3)
Angstrom,
beta = 90.3959(9)degrees, V = 3683.1(2) Angstrom(3), Z
= 8]. The
structure is built from layers maintained together via
hydrogen bonds.
Within a layer, squarate ligands act as linkers between
lanthanide and
potassium cations. The thermal decomposition of the precursors
has been
studied by powder thermodiffractometry and thermal analyses.
It is
shown that crystalline intermediate phases are formed
during the
degradation. Among them, unprecedented mixed anhydrous
squarates,
LnK(C4O4)(2), could be isolated. The crystal structure
of the Y
compound has been solved ab initio from X-ray powder diffraction
data,
using direct-space methods [a = 6.2010(5) Angstrom, c
= 11.639(l)
Angstrom, V = 447.55 Angstrom(3), Z = 2]. The structure
consists of
layers of edge-sharing YO8 and KO8 antiprisms, pillared
by
mu(8)-squarate groups. The end of the precursor decomposition
is marked
by the formation of cubic sesquioxides Ln(2)O(3), including
lanthanum
oxide.
DICVOL
2004-45
Zhang, Y Li, YD
Red photoluminescence and crystal structure of Sr3Y2(BO3)(4)
JOURNAL OF ALLOYS AND COMPOUNDS 384, 2004, 88-92.
The crystal structure of a new compound Sr(3)y(2)(BO3)(4) has been
determined from powder X-ray diffraction data by means
of the Rietveld
method. The structure can be described as being made up
of isolated
triangles, strontium-oxygen polyhedra, and yttrium-oxygen
polyhedra.
The yttrium atom has eight-fold coordination. The strontium
atoms have
10-, 9- and 8-fold coordination in a covalent matrix.
Sr(3)y(2)(BO3)(4):Eu phosphor exhibits a strong red emission
around 615
nm because Eu3+ ion locates at a non-centrosymmetric site
in the host
lattice. In particular, the compound Sr-3(Y0.9Eu0.1)(2)(BO3)(4)
has the
strongest emission intensity.
DICVOL
2004-46
Li, YQ de With, G Hintzen, H
Synthesis, structure, and luminescence properties of Eu2+ and Ce3+
activated BaYSi4N7
JOURNAL OF ALLOYS AND COMPOUNDS 385, 2004, 1-11.
BaYSi4N7 and its phosphors activated with Eu2+ and Ce3+ were
synthesized by solid-state reaction at 1400-1650 degreesC
under
nitrogen mixed with hydrogen atmosphere. The crystal structure
of
BaYSi4N7 was solved by direct methods and refined by the
Rietveld
method from powder X-ray diffraction data. BaYSi4N7 crystallizes
in the
hexagonal space group P6(3)mc (No.186), with a = 6.0550
(2) Angstrom, c
= 9.8567 (1) Angstrom, V = 312.96 (2) Angstrom(3). and
Z = 2. which is
isotypic with BaYbSi4N7. The photoluminescence properties
have been
studied for the solid solutions of Ba1-xEuxYSi4N7 (x =
0-0.4) and
BaY1-xCexSi4N7 (x = 0-0.1) at room temperature. Eu2+-doped
BaYSi4N7
gives a broad green emission band centered between 503
and 527 nm
depending on the Eu2+ concentration. The Eu2+ emission
band shows a
red-shift formulation with increasing Eu2+ concentration
mainly caused
by the change of the crystal field strength and Stokes
shift.
Concentration quenching of Eu2+ emission is observed for
x = 0.05 due
to energy transfer between Eu2+ ions by electric dipole-dipole
interactions with a critical interaction distance of about
20 Angstrom.
Ce3+-doped BaYSi4N7 exhibits a bright blue emission band
with a maximum
at about 417 nm, which is independent of Ce3+ concentration.
This is
ascribed to a lower solubility of Ce3+ ions in BaYSi4N7
lattice as
shown by X-ray powder diffraction analysis.
DICVOL, direct methods
2004-47
Matsuda, R Kitaura, R Kitagawa, S
Kubota, Y Kobayashi, TC
Horike, S Takata, M
Guest shape-responsive fitting of porous coordination polymer with
shrinkable framework
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126, 2004, 14063-14070.
In situ synchrotron X-ray powder diffraction patterns of porous
coordination polymers {[Cu-2-(pzdc)(2)(bpy)](.)G} have
been measured
(pzdc = pyrazine-2,3-dicarboxylate, bpy = 4,4'-bipyridine)
(where G =
H2O for CPL-2 superset of H2O, G = benzene for CPL-2 superset
of
benzene, and G = void for the apohost). The structures
of apohost and
CPL-2 superset of benzene were determined from Rietveld
analysis.
Adsorption of benzene in the channels induced a remarkable
contraction
in the crystal (b axis; 6.8%, volume; 4.9%), although
the channels were
occupied by the benzene molecules. This crystal transformation
provides
a new pore structure that is well suited for benzene molecules,
and we
denote it as a "shape-responsive fitting" transformation.
This type of
pore gives rise to a new guideline: frameworks can be
composed of
flexible motifs that are linked via strong bond and/or
stiff motifs
that are connected via weaker bonds.
DICVOL
2004-48
Salamakha, PS Sologub, OL Rizzoli, C
Hester, JR Stepien-Damm, J
Goncalves, AP Lopes, EB Almeida,
M
Ternary RPt4B (R = La, Ce, Pr, Nd) compounds; structural and physical
characterisation
INTERMETALLICS 12, 2004, 1325-1334.
The compounds RPt4B, with (R = La, Ce, Pr, Nd), were synthesized and
their crystal structure was studied either by single crystal
X-ray
diffraction and/or by conventional and synchrotron X-ray
powder
diffraction. All four compounds of this family are isostructural
and
belong to the CeCo4B structure type. AC-susceptibility
and
magnetization studies show that: there is no magnetic
ordering of the
La compound down to 1.7 K; the Ce compound presents an
antiferromagnetic-type-transition at 2.4 K; and both Pr
and Nd
compounds present a ferromagnetic-type transition at 4.2
and 4.9 K,
respectively. Electrical resistivity studies show metallic
behaviour
for all compounds, the temperature dependence for the
La compound being
described by the Bloch Gruneisen relation. Thermopower
studies as a
function of temperature show that the thermopower is positive
and small
for these compounds, which is consistent with hole dominated
metallic
behaviour.
DICVOL
2004-49 ????????
Kitaura, R Iwahori, F Matsuda, R
Kitagawa, S Kubota, Y
Takata, M Kobayashi, TC
Rational design and crystal structure determination of a 3-D
metal-organic jungle-gym-like open framework
INORGANIC CHEMISTRY 43, 2004, 6522-6524.
A new three-dimensional (3-D) jungle-gym-like open metal-organic
framework has been synthesized from a two-dimensional
(2-D) layer
compound using a heterogeneous pillar insertion reaction.
Both the
starting 2-D layer and the resulting 3-D open compounds
have been
characterized using X-ray crystallography.
DICVOL
2004-50
Johnston, A Florence, AJ Shankland, K
Markvardsen, A
Shankland, N Steele, G Cosgrove,
SD
Powder study of
N-[2-(4-hydroxy-2-oxo-2,3-dihydro-1,3-benzothiazol-7-yl)ethyl]-3-[2-(2-n
aphthalen-1-ylethoxy)ethylsulfonyl]propylaminium benzoate
ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE 60, 2004,
O1751-O1753.
The crystal structure of the title compound, C26H31N2O5S2+.-C7O2H5-,
also known as AR-C69457CC, was solved by simulated annealing
from
laboratory X-ray powder diffraction data collected at
room temperature
to 2.1 Angstrom resolution. Subsequent Rietveld refinement
yielded an
R-wp of 0.038 and site-occupancy factors for the disordered
anion
components of 0.5.
DICVOL, Simulated annealing
2004-51
Grzechnik, A Dmitriev, V Weber, HP
Gesland, JY van Smaalen, S
LiSrAlF6 with the LiBaCrF6-type structure
JOURNAL OF PHYSICS-CONDENSED MATTER 16, 2004, 3005-3013.
The crystal structure of LiSrAlF6-III (P2(1)/c, Z = 4) occurring above
3.0 GPa at room temperature was studied with synchrotron
angle-dispersive x-ray powder diffraction in a diamond
anvil cell. It
was solved by combining a global optimization and a topological
analysis with the Rietveld method using rigid-body AlF6
geometrical
constraints. LiSrAlF6-III, related to LiBaCrF6 (P2(1)/c,
Z = 4), is
built of deformed SrF12 icosahedra within a three-dimensional
framework
of corner-sharing distorted AlF6 octahedra and LiF4 tetrahedra,
whereas
the low-pressure phases I (P (3) over bar 1c, Z = 2) and
II (P2(1)/c, Z
= 4) have cations exclusively in distorted octahedral
coordinations.
The pressure-induced changes of the coordination polyhedra
in the
series LiSrAlF6-I, LiSrAlF6-II to LiSrAlF6-III are similar
to the
differences in coordination polyhedra due to the increase
of the ionic
radii of the Sr2+ and Ba2+ cations in LiSrAlF6-I and LiBaM"F-6
(M" =
At, Ga, Cr, V, Fe, or Ti) at ambient conditions. These
observations are
discussed on the basis of the high-pressure high-temperature
systematics in AB(2)X(6) compounds.
DICVOL
2004-52
Serre, C Millange, F Surble, S Greneche,
JM Ferey, G
Synthesis, characterization, and properties of an open-framework
iron(III) dicarboxylate: MIL-85 or
(Fe2O)-O-III{O2C-CH3}(2){O2C-C6H4-CO2} . 2CH(3)OH
CHEMISTRY OF MATERIALS 16, 2004, 2706-2711.
A new three-dimensional iron(III) dicarboxylate, MIL-85 or
(Fe2O)-O-III{O2C-CH3}2{O2C- C6H4-CO2}.2CH(3)OH, has been
obtained under
solvothermal conditions, and its structure was determined
using X-ray
powder diffraction data. Its chiral framework is built
up from helical
chains of iron(III) octahedra linked through terephthalate
dianions.
This creates a three-dimensional structure with an array
of 1-D
small-pore channels filled with free and bound methanol
moieties. The
thermal behavior has been investigated using TGA, and
X-ray
thermodiffractometry indicates that MIL-85 is stable up
to 275 degreesC
with a fully reversible departure of solvent process.
When the free and
bound solvent molecules are removed, a nanoporous solid
with a Langmuir
surface area of 110 m(2)/g is obtained. Mossbauer spectrometry
confirms
the presence of high-spin-state Fe3+ within the structure
and a change
in the iron environment upon solvent departure. Finally,
one can
conclude from magnetic data that MIL-85 exhibits a frustrated
magnetic
behavior in the low-temperature range. Crystal data for
MIL-85:
hexagonal space group P6(1) (no. 169) with alpha = 11.045
(1) Angstrom,
c = 18.823 (1) Angstrom, and Z = 6.
DICVOL
2004-53
Kaduk, JA
Crystal structure of guaifenesin, 3-(2-methoxyphenoxy)-1,2-propanediol
POWDER DIFFRACTION 19, 2004, 127-132.
The crystal structure of the common expectorant guaifenesin,
3-(2-methoxyphenoxy)-1, 2-propanediol (C10H14O4) was solved
by applying
Monte Carlo simulated annealing techniques to synchrotron
powder data,
and refined using the Rietveld method. Initial structure
solutions
yielded an unreasonable conformation, and an unacceptable
refinement.
Quantum chemical geometry optimizations were used to identify
the
correct conformation. Guaifenesin crystallizes in the
orthorhombic
space group P2(1)2(1)2(1) (#19), with a=7.65705(7), b=25.67020(24),
c=4.97966(4) Angstrom, V=978.79(2) Angstrom(3), and Z=4.
Both hydroxyl
groups act as hydrogen bond donors and acceptors, resulting
in the
formation of a two-dimensional network of strong hydrogen
bonds in the
ac plane. The solid state conformation is similar to4
kcal/mol higher
in energy than the minimum-energy conformation of an isolated
molecule,
but the formation of the hydrogen bonds results in an
energy gain of
similar to100 kcal/mol. Knowledge of the crystal structure
permits
quantitative phase analysis of guaifenesin-containing
pharmaceuticals
(such as Duratuss GP 120-1200) by the Rietveld method.
DICVOL
2004-54
Audebrand, N Jeanneau, E Bataille, T
Raite, S Louer, D
A family of microporous mixed oxalates with isotypic-framework
structures based on eight-coordinate metals
SOLID STATE SCIENCES 6, 2004, 579-591.
Structural relationships between mixed oxalates with crystal structures
consisting of isotypic anionic frameworks [MM'(C2O4)(4)](2-)
built from
dodecahedrally coordinated M and M' metals, with counter
cations
located in tunnels, are described. The principles of a
predictive
structural derivation, based on the YK(C2O4)(2)(.)4H(2)O
structure
type, is presented. Four new phases with isotypic frameworks
that
conform to the classification and to a proposed empirical
six-valence-sum rule are reported. The new oxalates have
been
synthesised from mild chemistry and their crystal structures
have been
determined from single-crystal or powder diffraction data.
Crystal data
for the new phases are: CdZrSr(C2O4)(4)(.)6H(2)O, S.G.
I (4) over bar
m2, a = 11.2362(4) Angstrom, c = 8.6084(3) Angstrom, Z
= 2;
InK(C2O4)(2)(.)4H(2)O, S.G. I4(1)/a, a = 11.0549(3) Angstrom,
c =
8.9735(3) Angstrom, Z = 4; YRb(C2O4)(2)(.)4H(2)O, S.G.
I4(1)/a, a =
11.4569(3) Angstrom, c = 9.1502(4) Angstrom, Z = 4;
Ca2Zr(C2O4)(4)(.)5.5H(2)O, S.G. I (4) over bar m2, a =
11.2558(2)
Angstrom, c = 8.4288(2) Angstrom, Z = 2. The open-framework
structures
of all phases can be described on the basis of building
walls made of
mixed dodecahedra MO8 and M'O-8, connected through bichelating
oxalate
groups. The third element is located in channels with
an elliptic
cross-section. The thermal behaviour of all phases is
studied from
thermogravimetry and thermodiffractometry. It is shown
that the
dehydration process is somewhat related to the structure
features and
depends on the valence of the counter cation. In all cases,
zeolite-type properties involving weakly bonded water
molecules are
pointed out.
DICVOL
2004-55
Mora, AJ Delgado, GE Pineda, C Tinoco,
T
Synthesis and structural study of the AgIn5Te8 compound by X-ray powder
diffraction
PHYSICA STATUS SOLIDI A-APPLIED RESEARCH 201, 2004, 1477-1483.
The AgIn5Te8 compound was synthesized by the melt and annealing
technique and its structure was refined from X-ray powder
diffraction
pattern using the Rietveld method. AgIn5Te8 crystallizes
in the
tetragonal space group R (4) over bar 2m (N-o 111), Z
= 1, with a =
6.1952(2) Angstrom, c = 12.419(4) Angstrom, V = 476.7(2)
Angstrom(3).
The refinement of 23 instrumental and structural parameters
led to R-p
= 8.2%, R-wp = 11.6%, R-exp = 6.8% and S = 1.7; R-B =
11.2% for 5501
step intensities and 253 independent reflections. The
structure is
characterized by a double alternation of selenide-metal
planes
according to the In-2-Te-1-In-1-Te-2-Ag-Te-2-In-1-Te-1-In-2
sequence.
DICVOL
2004-56
Wu, L Wang, C Chen, XL Li, XZ
Xu, YP Cao, YG
Ab initio structure determination of new compound Li4CaB2O6
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 1847-1851.
A new compound, Li(4)WaB(2)O(6), has been synthesized by solid-state
reaction and its structure has been determined from powder
X-ray
diffraction data by direct methods. The refinement was
carried out
using the Rietveld methods and the final refinement converged
with R-p
= 10.4% R-wp = 14.2%, R-exp = 4.97%. This compound belongs
to the
orthorhombic space group Pnnm, with lattice parameters
a 9.24036(9)
Angstrom, b = 8.09482(7) Angstrom, and c = 3.48162(4)
Angstrom.
Fundamental building units are isolated [BO3](3-) anionic
groups, which
are all parallel to the a-b plane stacked along the c-axis.
The Ca
atoms are six-coordinated by the O atoms to form octahedral
coordination polyhedra, which are joined together through
edges along
the c-axis, forming infinitely long three-dimensional
chains. The Li
atoms have a four-fold and a five-fold coordination with
O atoms that
lead to complex Li-O-Li chains that also extend along
the c-axis. The
infrared spectrum of Li4CaB2O6 was also studied, which
is consistent
with the crystallographic study.
DICVOL
2004-57
Li, XJ Kobayashi, T Zhang, FX Kimoto,
K Sekine, T
A new high-pressure phase of LiAlO2
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 1939-1943.
A new high-pressure phase of LiAlO2 has been recovered through a shock
recovery technique at pressures above 9 GPa. This new
phase has been
refined as a tetragonal structure with lattice parameters
of a =
0.38866(8) nm and c = 0.83001(18) nm. Its calculated density
is 3.51
g/cm(3). about 34% denser than gamma-LiAlO2. The aluminum
and lithium
cations in this new phase are six-fold coordinated, as
in alpha-LiAlO2,
and the structure of this new phase is similar to tetragonal
LiFeO2.
This new high-pressure phase is stable at temperatures
up to 773 K.
DICVOL
2004-58
Devi, RN Wormald, P Cox, PA Wright,
PA
Novel pillared aluminum ethylene diphosphonate displaying reversible
dehydration-rehydration behavior
CHEMISTRY OF MATERIALS 16, 2004, 2229-2237.
The novel aluminum ethylene diphosphonate
Al-2(OH)(2)(H2O)(2)(O3PCH2CH2PO3) has been synthesized
hydrothermally..
It crystallizes in the triclinic space group (P (1) over
bar; a =
8.5977(10), b = 7.0499(3), c = 9.5290(4) Angstrom; alpha
= 89.997(21),
beta = 104.321(8), gamma = 114.225(11)degrees; V =
506.98(8)Angstrom(3)) with aluminophosphonate layers similar
to those
found in Al(OH)(H2O)CH3PO3 linked via ethylene (-CH2CH2-)
groups. The
solid loses water upon heating in two steps, the first
at 100 degreesC
and the second at 360 degreesC. The first water loss leaves
a
crystalline solid with a framework structure of
Al-2(OH)(2)(O3PCH2CH2PO3) closely related to that of the
parent (C2/ c;
a = 15.3723(21), b = 6.7613(8), c = 9.7374(13) Angstrom;
beta =
102.392(9)degrees; V = 988.4438 Angstrom(3)) whereas the
second water
loss results in major loss of crystallinity. X-ray powder
diffraction
has been used to determine and refine the structures of
the parent and
intermediate dehydrated phases. The main structural difference
is the
loss of one water molecule bound to aluminum, which changes
the metal
cation's coordination from octahedral to distorted square
planar. The
as-prepared and dehydrated samples have been simulated
computationally.
The transformation has been monitored by in-situ Al-27
MAS NMR
spectroscopy; octahedral aluminum (delta(iso) = -7.1 ppm;
asymmetry
parameter, eta = 1.0; quadrupolar coupling constant, QCC
= 5.4 MHz) is
converted to 5-fold coordinated aluminum (delta(iso) =
20.7 ppm; eta =
0; QCC = 5.8 MHz) by heating at 130 degreesC for 1 h.
The process is
fully reversible.
DICVOL
2004-59
Serre, C Millange, F Thouvenot, C
Gardant, N Pelle, F Ferey, G
Synthesis, characterisation and luminescent properties of a new
three-dimensional lanthanide trimesate: M((C6H3)-(CO2)(3))
(M = Y, Ln)
or MIL-78
JOURNAL OF MATERIALS CHEMISTRY 14, 2004, 1540-1543.
A new three-dimensional europium-doped yttrium
1,3,5-benzenetricarboxylate has been obtained under hydrothermal
conditions. The structure of MIL-78(Y, Eu) or Y1-xEux((C6H3)-(CO2)(3))
(x similar to 0.024) has been solved from X-ray powder
diffraction data
(a = 6.941(1) Angstrom, b similar to 14.700(2) Angstrom,
c = 8.488(1)
Angstrom, beta = 107.73(1) degrees, V = 824.9(4) Angstrom(3),
space
group C2/m (no. 12)). Its structure is built up from chains
of
edged-sharing eight-coordinated monocapped square antiprism
polyhedra
and trimesate anions, creating a three-dimensional structure.
The same
structure is formed by replacing yttrium by a rare-earth
element. The
thermal behaviour of MIL-78(Y, Eu) has been investigated
using TGA and
X-ray thermodiffractometry and indicates that MIL-78(Y,
Eu) is stable
up to 450 degreesC. The study of the optical properties
of samples
doped with different rare-earths reveals strong fluorescence
under VUV
radiation.
DICVOL
2004-60
Cerny, R Renaudin, G Favre-Nicolin, V
Hlukhyy, V Pottgen, R
Mg1+xIr1-x (x=0, 0.037 and 0.054), a binary intermetallic compound
with
a new orthorhombic structure type determined from powder
and
single-crystal X-ray diffraction
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 60, 2004, 272-281.
The new binary compound Mg1 + xIr1-x (x = 0-0.054) was prepared by
melting the elements in the Mg:Ir ratio 2:3 in a sealed
tantalum tube
under an argon atmosphere in an induction furnace (single
crystals) or
by annealing cold-pressed pellets of the starting composition
Mg:Ir 1:1
in an autoclave under an argon atmosphere (powder sample).
The
structure was independently solved from high-resolution
synchrotron
powder and single-crystal X-ray data: Pearson symbol oC304,
space group
Cmca, lattice parameters from synchrotron powder data
a = 18.46948 (6),
b = 16.17450 (5), c = 16.82131 (5) Angstrom. Mg1-xIr1-x
is a
topologically close-packed phase, containing 13 Ir and
12 Mg atoms in
the asymmetric unit, and has a narrow homogeneity range.
Nearly all the
atoms have Frank-Kasper-related coordination polyhedra,
with the
exception of two Ir atoms, and this compound contains
the shortest
Ir-Ir distances ever observed. The solution of a rather
complex crystal
structure from powder diffraction, which was fully confirmed
by the
single-crystal method, shows the power of powder diffraction
in
combination with the high-resolution data and the global
optimization
method.
DICVOL
2004-61
Li, XZ Chen, XL Wu, L Cao, YG
Zhou, T Xu, Y
Ba3YB3O9: phase transition and crystal structure
JOURNAL OF ALLOYS AND COMPOUNDS 370, 2004, 53-58.
A new modification of the compound Ba3YB3O9, beta phase, has been
attained through solid phase transition from alpha phase
at
1125-1134degreesC. beta-Ba(3)yB(3)O(9) crystallizes in
the hexagonal
space group R3 with cell parameters a = 13.0529(8) (A)
over circle, c =
9.5359(9) (A) over circle. The crystal structure of alpha-Ba3YB3O9
has
been determined from powder X-ray diffraction (XRD) data.
The
refinement was carried out using the Rietveld methods
and the final
refinement converged with R-p = 8.8%, and R-wp = 11.8%
with R-exp =
5.65%. In its structure, the isolated [BO3](3-) anionic
groups are
parallel to each other and distributed layer upon layer
along the
c-axis. The Y atoms are six-coordinated by the O atoms
to form
octahedra. The result of IR spectrum confirmed the existence
of
[BO3](3-) triangular groups.
DICVOL
2004-62
Zhang, Y Li, YD
Red photoluminescence properties and crystal structure of sodium rare
earth oxyborate
JOURNAL OF ALLOYS AND COMPOUNDS 370, 2004, 99-103.
The subsolidus phase relations of the system Y2O3-Na2O-B2O3 are
reported. There are seven binary compounds and two ternary
compounds in
this system. A new ternary compound Na2Y2B2O7 is identified.
The
structure has been determined for the compound Na2Y2B2O7
from powder
X-ray diffraction. The lattice constants of P2(1)/c for
the compound
Na2Y2B2O7 are a = 10.5993 (1) (A) over circle, b = 6.2311
(1) (A) over
circle, c = 10.2247(1) (A) over circle, beta = 117.756(1)degrees
and z
= 4. The structure can be described as being made up of
isolated BO3
triangles and YO8 polyhedra. The photoluminescence properties
of Eu
ion-doped Na2Y2B2O7 and Na3Y(BO3)(2) show strong red-emission
of the
D-5(0)-F-7(2) transitions at 611 and 615 nm, respectively.
The results
of emission spectra are in good agreement with the crystallographic
study. The relationship between Eu ion content and emission
intensity
is analyzed too.
DICVOL
2004-63 ??
Serre, C Pelle, F Gardant, N Ferey,
G
Synthesis and characterization of MIL-79 and MIL-80: Two new
luminescent open-framework rare-earth dicarboxylates with
unusual 1D
inorganic subnetworks
CHEMISTRY OF MATERIALS 16, 2004, 1177-1182.
Two new three-dimensional europium(III) dicarboxylates, MIL-79 or
EU5(III)(OH)(9)(H2O)(6)-(O2C-C2H2-CO2)(3)(.)9.5H(2)O,
and MIL-80 or
EU4III(OH)(4)(H2O)(5)(O2C-C2H2-CO2)(4)(.)4H(2)O, have
been obtained
under hydrothermal conditions. Both structures, which
have been
determined using either X-ray powder or single-crystal
diffraction
data, are built-up from unusual complex chains made from
clusters of
eight-, nine-, and ten-coordinated europium(III) polyhedra
linked
through fumarate and maleate dianions. This creates three-dimensional
structures with either I-D large elongated pore channels
(MIL-79) or
cages (MIL-80) filled in both cases with free water molecules
which
interact with terminal water molecules or apical oxygen
atoms from the
carboxylates. The thermal behavior of MIL-79 has been
investigated
using TGA and X-ray thermodiffractometry and reveals that
its
dehydration leads to an irreversible pore contraction.
Study of the
luminescence properties of the yttrium(III) form of MIL-79
doped with
europium(III) reveals a significant red-emission upon
VUV radiation.
Crystal data for MIL-79: monoclinic space group C2/m with
a = 25.954(1)
Angstrom, by = 11.014(1) Angstrom, c = 13.247(1) Angstrom,
beta =
119.162(1)degrees, and Z = 4. Crystal data for MIL-80:
triclinic space
group P (1) over bar with a = 10.5770(2) Angstrom, b =
10.6164(2)
Angstrom, c = 14.9403(3) Angstrom, alpha = 91.624(1)degrees,
beta =
91.120(1)degrees, gamma = 113.892(1)degrees, and Z = 2.
DICVOL
2004-64
Couhorn, U Dronskowski, R
Alkali-metal meta-hydroxyphenolates: Syntheses and crystal structures
from powder X-ray diffraction
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 630, 2004, 427-433.
M[M-C6H4O(OH)] (M = Li-Cs) have been obtained as highly air- and
moisture-sensitive powders from reaction mixtures of the
appropriate
alkali metals and resorcinol in thf. Both the potassium
and rubidium
compounds were structurally characterized by means of
powder X-ray
diffraction using the Simulated Annealing method and the
Rietveld
profile refinement technique including C-C/C-O bond distance
and C-C-C
angle restraints. K[m-C6H4O(OH)] (orthorhombic P2(1)2(1)2(1))
forms
infinite alternating chains of meta-hydroxyphenolate anions
connected
by K-O bonds and short charge-assisted hydrogen bonds,
thereby
generating a three-dimensional network of corrugated layers
similar to
the structure of pure resorcinol. The potassium cations
are surrounded
by a triangle of oxygen and, moreover, coordinated by
six adjacent
phenylene rings to form a distorted octahedron. The complex
crystal
structure of Rb[m-C6H4O(OH)] (monoclinic Pa) is characterized
by layers
of hydrogen-bonded meta-hydroxyphenolate triple units
separated by
corrugated rubidium layers. The three crystallographically
different Rb
atoms are coordinated by three, four, and five oxygens
with irregular
polyhedra, and the rubidiums are also involved in further
electrostatic
interactions by up to eight phenylene rings.
DICVOL
2004-65
Guillou, N Livage, C van Beek, W
Ferey, G
Ab initio determination of a new complex structure (55 non-hydrogen
atoms) from synchrotron powder data: An uncommon nickel
succinate,
Ni-7(C4H4O4)(4)(OH)(6)(H2O)(3) . 7H(2)O
EUROPEAN POWDER DIFFRACTION EPDIC 8 443-4, 2004, 333-336.
Ni-7(C4H4O4)(4)(OH)(6)(H2O)(3)(.)7H(2)O, a new layered nickel(II)
succinate, was prepared hydrothermally (180degreesC, 48
h, autogenous
pressure) from a 1:1.5:4.1:120 mixture of nickel (II)
chloride
hexahydrate, succinic acid, potassium hydroxide and water.
It
crystallizes in the monoclinic system (space group P2(1)/c,
Z = 4) with
the following parameters a = 7.8597(1) Angstrom, b = 18.8154(3)
Angstrom, c = 23.4377(4) Angstrom, beta= 92.0288(9)degrees,
and V=
3463.9(2) Angstrom(3). Its structure, which contains 55
non-hydrogen
atoms, was solved ab initio from synchrotron powder diffraction
data.
It can be described from hybrid organic-inorganic layers,
constructed
from nickel oxide corrugated chains. These chains are
built up from
NiO6 hexameric units connected via a seventh octahedron.
Half of the
succinates decorate the chains, and the others connect
them to form the
layers. The three dimensional arrangement is ensured by
hydrogen bonds
directly between two adjacent layers and via free water
molecules.
DICVOL
2004-66
Zaske, L Perrin, MA Daiguebonne, C
Guillou, O
Docetaxel (Taxotere (R) Trihydrate) forms: Crystal structure
determination from XRPD & XRSCD data
EUROPEAN POWDER DIFFRACTION EPDIC 8, 443-4, 2004, 411-414.
Docetaxel (form A), a stoichiometric hydrate containing three water
molecules per molecule of drug substance (Taxoteree),
is
thermodynamically stable under ambient conditions of pressure,
temperature and relative humidity. In order to gain a
better
understanding of docetaxel system at the atomic scale
a structural
study was performed. Due to strong anisotropy of crystals
(thin
plates), the crystal structure of docetaxel (29 degrees
of freedom) was
solved and refined using high resolution XRPD data applying
an ab
initio direct space method. In parallel, an in-depth crystal
growth
study was carried out until single crystals suitable for
XRSCD
structural resolution were obtained: surprisingly, a new
polymorph of
docetaxel, called form B, was isolated.
DICVOL
2004-67
Albesa-Jove, D Kariuki, BM Kitchin, SJ
Grice, L Cheung, EY Harris, KDM
Challenges in direct-space structure determination from powder
diffraction data: A molecular material with four independent
molecules
in the asymmetric unit
CHEMPHYSCHEM 5, 2004, 414-418.
DICVOL, GENETIC ALGORITHM
2004-68
Grzechnik, A Dmitriev, V Weber, HP
Gesland, JY van Smaalen, S
The crystal structures of pressure-induced LiSrAlF6-II and LiCaAlF6-II
JOURNAL OF PHYSICS-CONDENSED MATTER 16, 2004, 1033-1043.
The crystal structures of LiCaAlF6-II and LiSrAlF6-II (both P2(1)/c,
Z
= 4) occurring at high pressures and room temperature
were studied with
synchrotron angle-dispersive x-ray powder diffraction
in diamond anvil
cells. The structure of LiSrAlF6-II stable between 1.6
and 3.0 GPa was
solved with a global optimisation algorithm and group
theory
considerations, and refined with the Rietveld method in
the rigid-body
approximation. It is a distorted variant of the ambient
pressure
polymorph (LiSrAlF6-I, <P(3)over bar1c>, Z = 2), in
which each cation
occupies a deformed octahedral site. LiCaAlF6 transforms
to this
monoclinic polymorph II above about 7 GPa. The differences
in the
high-pressure behaviours of LiCaAlF6 and LiSrAlF6 are
discussed by
considering the ionic radii.
DICVOL
2004-69
Muangsin, N Prajuabsook, M Chimsook, P
Chantarasiri, N
Siraleartmukul, K Chaichit, N
Hannongbua, S
Structure determination of diclofenac in a diclofenac-containing
chitosan matrix using conventional X-ray powder diffraction
data
JOURNAL OF APPLIED CRYSTALLOGRAPHY 37, 2004, 288-294.
The structure determination of diclofenac embedded in a
diclofenac-containing chitosan matrix using conventional
X-ray powder
diffraction data is demonstrated. It reveals that sodium
diclofenac,
the starting material in the preparation of a controlled-release
diclofenac-containing chitosan matrix, changes to diclofenac
acid in
space group C2/c in the matrix. Simple methods were employed
for
handling the sample to obtain X-ray powder diffraction
data of
sufficiently high quality for the determination of the
crystal
structure of diclofenac embedded in chitosan. These involved
grinding
and sieving several times through a micro-mesh sieve to
obtain a
suitable particle size and a uniformly spherical particle
shape. A
traditional technique for structure solution from X-ray
powder
diffraction data was applied. The X-ray diffraction intensities
were
extracted using Le Bail's method. The structure was solved
by direct
methods from the extracted powder data and refined using
the Rietveld
method. For comparison, the single-crystal structure of
the same drug
was also determined. The result shows that the crystal
structure solved
from conventional X-ray powder diffraction data is in
good agreement
with that of the single crystal. The deviations of the
differences in
bond lengths and angles are of the order of 0.030 Angstrom
and
0.639degrees, respectively.
DICVOL
2004-70
Nowell, H Attfield, JP
X-Ray and neutron powder diffraction studies of the crystal structure
of vitamin K-3
NEW JOURNAL OF CHEMISTRY 28, 2004, 406-411.
The previously unknown structure of vitamin K-3 (menadione,
2-methyl-1,4-naphthoquinone, C11H8O2), a synthetic compound
from which
it is possible to derive the naturally occurring K vitamins,
has been
solved from X-ray powder diffraction data. Solution was
achieved using
simulated annealing and restrained Rietveld refinement,
using
restraints derived from similar known structures. Further
refinement
has been carried out using neutron diffraction data; this
confirmed the
molecular packing and allowed further insight into the
structural
detail with regard to methyl group orientation, thus allowing
the
proposal of an extensive C - H...O hydrogen bonding scheme
by reference
to comparable known structures. The crystal structure
consists of
chains of molecules lying head-to-tail. This study may
aid the
understanding of the biological activity of vitamin K.
DICVOL
2004-71
Li, XZ Chen, XL Jian, JK Wu, L
Xu, YP Cao, YG
Thermal stability and crystal structure of beta-Ba3YB3O9
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 216-220
A new compound, beta-Ba3YB3O9, has been attained through solid phase
transition from alpha-Ba3YB3O9 at high temperatures. Differential
thermal analysis (DTA) revealed the phase transition at
about
1120degreesC, the melting temperature at about 1253degreesC.
Its
crystal structure has been determined from powder X-ray
diffraction
data. The refinement was carried out using the Rietveld
method and the
final refinement converged with R-p = 10.5% and R-wp =
13.7%. This
compound belongs to the hexagonal space group R-3, with
lattice
parameters a = 13.0441(1) Angstrom and c = 9.5291(1) Angstrom.
There
are 6 formulas per unit cell and 7 atoms in the asymmetric
unit. The
structure of beta-Ba3YB3O9 is built up from Ba(Y)O-8,
BaO6 and YB6O18
units formed by one YO6 octahedron and six BO3 triangles
with shared O
atoms.
DICVOL
2004-72
Graham, D Kennedy, AR McHugh, CJ
Smith, WE David, WIF
Shankland, K Shankland, N
The crystal structures of three primary products from the selective
reduction of 2,4,6-trinitrotoluene
NEW JOURNAL OF CHEMISTRY 28, 2004, 161-165
The crystal structures of three primary products from the selective
reduction of 2,4,6-trinitrotoluene (TNT) have been determined
by
synchrotron X-ray powder diffraction (2-amino-4,6-dinitrotoluene)
and
single crystal X-ray diffraction (4-amino-2,6-dinitrotoluene
and
2-hydroxyamino-4,6-dinitrotoluene). The molecular structure
of
2-amino-4,6-dinitrotoluene, including rotational disorder
of the
6-nitro group, was subsequently detailed to a higher resolution
by a
single-crystal analysis. In contrast to the known structures
of TNT,
the crystal structures of these amino species are dominated
by
hydrogen-bonded sheets connected via ring stacking, whilst
that of
2-hydroxyamino-4,6-dinitrotoluene is dominated by the
dual
hydrogen-bonding acceptor/donator role of the hydroxyamine
group.
DICVOL, Sync
2004-73
Kavecansky, V Mihalik, M Mitroova, Z
Lukacova, M
Neutron diffraction study of crystal and magnetic structure of
Dy[Fe(CN)(6)].4D(2)O
CZECHOSLOVAK JOURNAL OF PHYSICS, 54, suppl D, part 2, 2004, D451-D574.
We present an analysis of the powder neutron diffraction patterns taken
from the Dy[Fe(CN)(6)]. 4D(2)O at room temperature and
in the
temperature range 1.6 - 40 K. The deuterium positions
were localized by
means of combination of direct and reciprocal space methods
and crystal
structure of the compound was refined using the Rietveld
method. The
knowledge of the complete crystal structure, including
the deuterium
atoms positions, enables further investigation of magnetic
structure of
these types of materials from the neutron diffraction
experiments. The
investigated phase was found to order magnetically bellow
2.8 K. The
diffraction patterns taken at temperatures 1.76 K - 9.63
K show gradual
development of magnetic moment as temperature decreases.
2004-74
Baerlocher, C McCusker, LB Prokic, S
Wessels, T
Exploiting texture to estimate the relative intensities of overlapping
reflections
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 219, 2004, 803-812.
Additional information about the relative intensities of reflections
that overlap in a powder diffraction pattern can be obtained
from a
polycrystalline sample in which the crystallites are preferentially
oriented. If the data are collected and analyzed appropriately,
more
single-crystal-like reflection intensities can be extracted,
and
thereby more complex structures solved. This 'texture
method' was
implemented initially in reflection mode and its power
demonstrated
with the solution of the 117-atom structure of the hi-h-silica
zeolite
UTD-1F However, the experiment required a minimum of 3
days of
synchrotron beamtime per sample. In an attempt to reduce
the amount of
beamtime needed and to simplify the experiment itself,
a transmission
mode alternative using an area detector was developed.
Details of the
sample preparation, data collection and data analysis
for both
geometries are described. The solution of the structures
of the
aluminophosphates Mu-9 (R(3) over bar c, a = 14.0696(1)
Angstrom, c =
42.3113(4) Angstrom) and AIPO-M (Pbca, a = 9.7493(1) Angstrom,
b =
29.1668(2) Angstrom, c = 9.3528(1) Angstrom) using reflection
and
transmission mode data, respectively, are provided as
examples of the
method.
2004-75
Bataille, T Audebrand, N Boultif, A
Louer, D
Structure determination of thermal decomposition products from
laboratory X-ray powder diffraction
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 219, 2004, 881-891.
Ab initio structure determination from powder diffraction data of
compounds resulting from solid state transformations is
still rather
limited. Two major factors influence the stages of the
structure
elucidation of these solids, i.e. the lower precision
in peak position
for indexing and the strong line overlap for extracting
integrated
intensities. The present study deals with the consideration
of these
two problems for solving the crystal structure of two
thermal-decomposition inorganic products, Nd(NO3)(3) (.)
4 H2O and
Pb3O2(NO3)(2). The new features of DICVOL04, as zero shift
refinement.
a priori zero search and tolerance of spurious lines have
been used for
indexing, several phases obtained during the thermal treatment
of
neodymium nitrate hexahydrate. The crystal structures
of Nd(NO3)(3) (.)
4 H2O and Pb3O2(NO3)(2) have been solved with the direct
methods and
the structure model of Pb3O(2)(NO3)(2) has been completed
using a
global optimisation approach. The monoclinic structure
of neodymium
nitrate tetrahydrate [a - 10.1744(4) Angstrom, b = 8.9716(5)
Angstrom,
c = 11.7295(5) Angstrom, beta = 97.384(4)degrees, V =
1061.80
Angstrom(3), S.G. P2(1)/c] is built from isolated ten-fold
coordinated
Nd polyhedra. The orthorhombic structure of lead oxide
nitrate [a =
7.6034(4) Angstrom, b = 5.7691(4) Angstrom, c = 18.5817(9)
Angstrom, V
= 815.09 Angstrom(3), S.G. Pnma] is built from double
chains of
edge-sharing OPb4 tetrahedra connected by nitrate groups.
In order to
estimate the chance of solving crystal structure of nanocrystalline
powdered compounds, a comparison of the efficiency of
direct methods
and direct-space approaches is made from powder diffraction
patterns
simulated for various crystallite sizes from the crystal
structure of
the decomposition product gamma-Zn2P2O7.
2004-76
Perchiazzi, N Ondrus, P Skala, R
Ab initio X-ray powder structure determination of parascorodite,
Fe(H2O)(2)AsO4
EUROPEAN JOURNAL OF MINERALOGY, 16, 2004, 1003-1007.
The crystal structure of parascorodite, Fe(H2O)(2)AsO4, has been solved
ab-initio from powder data. The mineral is trigonal, with
space group P
(3) over bar c1, Z = 6, a = 8.9232(2) Angstrom, c = 9.9296(3)
Angstrom.
The Rietveld refinement was led up to R-p = 4.5%. The
structure is
built up by the same coordination polyhedra found in its
dimorph
scorodite, namely slightly distorted Fe-centred octahedra
and
As-centred tetrahedra, but their connection lead to quite
different
crystal structures for the two polymorphs. Parascorodite
structure can
be described in terms of mixed octahedral-tetrahedral
"columns"
including Fe2 and As polyhedra, running along c, similar
to those found
in ferrinatrite and kaatialaite. These columns are interconnected
in a
threedimensional framework by the sharing of the O1 oxygen
between
[AsO4] tetrahedra and Fe1 octahedra, and by the strong
hydrogen bond
OW(...)O2.
2004-77
Golobic, A Skapin, SD Suvorov, D
Meden, A
Solving structural problems of ceramic materials
CROATICA CHEMICA ACTA 77, 2004, 435-446.
Methods for the crystal structure determination from powder diffraction
data are reviewed with special emphasis on the application
to technical
ceramics. Experimental techniques using other than laboratory
X-ray,
such as synchrotron radiation, neutron and electron beams,
are also
described. As an illustrative example, the crystal structure
determinations of compounds LaNbTiO6, La0.462Nb0.614Ti0.386O3
and
La0.37Nb0.889Ti0.111O3 in the ternary system of La2O3-Nb2O5-TiO2
are
reported.
2004-78
Garcia-Cuesta, MC Lozano, AM Melendez-Martinez,
JJ Luna-Giles, F
Ortiz, AL Gonzalez-Mendez, LM
Cumbrera, FL
Structure determination of nitrato-kappa O-bis[2-(2-pyridyl-kappa
N)amino-5,6-dihydro-4H-1,3-thiazine-kappa N]copper(II)
nitrate via
molecular modelling coupled with X-ray powder diffractometry
JOURNAL OF APPLIED CRYSTALLOGRAPHY 37, 2004, 993-999.
The title copper(II) coordination compound, C18H22CuN8O6S2 {[Cu(NO3)(
PyTz)(2)] NO3}, was synthesized in the form of small crystals
unsuitable for structure determination by single-crystal
X-ray
diffractometry. It was therefore characterized by molecular
modelling
coupled with X-ray powder diffractometry [ monoclinic,
space group
P2(1)/n, a = 20.695 (7) Angstrom, b = 8.054 (2) Angstrom,
c = 15.157
(4) Angstrom, beta = 112.09 (2)degrees and R-wp = 0.129].
The procedure
used to resolve the structure followed direct space methods
with a
'Monte Carlo/parallel tempering' search algorithm, where
the starting
configuration was obtained by means of molecular mechanics.
A final
refinement was performed with the Rietveld method. Bond
distances, bond
angles and torsion angles were compared with those of
similar compounds
deposited in the Cambridge Structural Database.
2004-79
Belik, AA Azuma, M Takano, M Lazoryak,
BI
SrF(e)2(PO4)(2): Ab initio structure determination with X-ray powder
diffraction data and unusual magnetic properties
CHEMISTRY OF MATERIALS 16, 2004, 4311-4318.
Structure of SrFe2(PO4)(2) was solved ab initio from X-ray powder
diffraction data (space group P2(1)/c (No. 14); Z = 4;
a = 9.3647(2) c,
b = 6.8518(l) Angstrom, c = 10.5367(2) Angstrom, and =
109.5140(8)degrees). It has almost linear tetrameric units
Fe2-Fe1-Fe1-Fe2 which join with each other through common
oxygen atoms
creating a complicated two-dimensional network parallel
to the bc
plane. Specific heat measurements revealed two phase transitions
at T-1
= 7.0 K and T-2 = 11.3 K in zero magnetic field. The phase
transition
at T-2 seems to be a structural phase transition. Magnetization
measurements showed that, below T-1, SrFe2(PO4)(2) exhibits
weak
ferromagnetism and demonstrates clear ferromagnetic hysteresis
loops.
Above 15 K, Curie-Weiss behavior was observed with an
effective
magnetic moment of 5.23 muB per Fe2+ ion and Weiss constant
of -18.9 K.
Weak ferromagnetic properties below T-1 can be explained
by canting of
antiferromagnetically ordered spins. Several field-induced
phase
transitions were observed in SrFe2(PO4)(2) at low temperatures.
2004-80
Peschar, R Pop, MM De Ridder, DJA
van Mechelen, JB
Driessen, RAJ Schenk, H
Crystal structures of 1,3-distearoyl-2-oleoylglycerol and cocoa butter
in the beta(V) phase reveal the driving force behind the
occurrence of
fat bloom on chocolate
JOURNAL OF PHYSICAL CHEMISTRY B 108, 2004, 15450-15453.
On the basis of high-resolution synchrotron powder diffraction data,
crystal structures have been solved for
1,3-distearoyl-2-oleoylglycerol, a major cis-mono-unsaturated
triglyceride fraction of cocoa butter, and cocoa butter
itself in the
beta(V) phase. The latter implies that in fact a crystal
structure
model of chocolate in the beta(V) phase has been obtained.
The results
clarify the metastability of the beta(V) phase and explain
why fat
bloom may develop on beta(V)-type chocolate that has been
stored at
temperatures that are too high.
2004-81 ???
Ikeda, T Akiyama, Y Oumi, Y Kawai,
A Mizukami, F
The topotactic conversion of a novel layered silicate into a new
framework zeolite
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 43, 2004, 4892-4896.
2004-82 ??????
Harvey, HG Herve, AC Hailes, HC
Attfield, MP
Synthesis, crystal structures, and modifications of novel framework
gallium diphosphonates
CHEMISTRY OF MATERIALS
The framework gallium diphosphonates 16, 2004, 3756-3766.
Ga-2[O3PC2H4PO3](H2O)(2)F-2.-2H(2)O (1) (triclinic, P1,
a = 5.0432(2)
Angstrom, b = 7.2468(3) Angstrom, c = 8.3499(4) Angstrom,
alpha =
107.489(2)degrees, beta = 92.444(2)degrees, gamma = 109.338(2)degrees,
Z =1) and Ga-2[O3PCH2(C6H4)CH2PO3](H2O)(2)F-2 (2) (triclinic,
P1, a =
4. 9673(l) Angstrom, b = 7. 0898(2) Angstrom, c = 10.
1220(3) Angstrom,
alpha = 92. 698(2)degrees, beta = 93.153(2)degrees, gamma
= 109.
122(2)degrees, Z = 1) and the solid-solution series
Ga-2{[O3PCH2(C6H4)CH2PO3](1-x)(HPO3)(2x)}(H2O)(2)F-2 (0
less than or
equal to X less than or equal to 0. 146) x = 0.541 (3)
and x = 0.144
Ga-2{[O3PCH2(C6H4)CH2PO3](0.853(6))(HPO3)(0.29(1))}(H2O)(2)F-2
(4)
(triclinic, P1, a = 4.959(2) Angstrom, b = 7.078(2) Angstrom,
c =
10.024(3) Angstrom,alpha = 92.404(5)degrees, beta = 92.955(5)degrees,
gamma = 109.187(5)degrees, Z = 1) have been synthesized
by solvothermal
methods and their structures determined using X-ray diffraction
data.
All the materials contain linear chains of corner-sharing
GaO4F2
octahedra that are linked by the diphosphonate groups
to form framework
structures. The channels of 1 are found to contain two
water molecules
per unit cell while those in 2 are too narrow to contain
extraframework
species. The apertures created in the phosphite-substituted
derivatives
of 2 (3 and 4) are shown, by crystallographic methods,
to be
considerably larger than those in 2 and, by thermogravimetric
methods,
to create more open structures. The synthetic conditions
or form of the
diphosphonate group are found to play a defining role
in the adoption
of this particular configuration of the inorganic component
in the
reported compounds and provide an additional strategy
for the rational
design of framework hybrid organic -inorganic solids.
2004-83
Dikarev, EV Shpanchenko, RV Andreini, KW
Block, E Jin, J Petrukhina, MA
Powder diffraction study of a coordination polymer comprised of rigid
building blocks: [Rh-2(O2CCH3)(4) . mu(2)-Se2C5H8-Se,Se
'](infinity)
INORGANIC CHEMISTRY 43, 2004, 5558-5563.
The crystal structure of a new hybrid product comprised of two rigid
building blocks, namely dirhodium(II) tetraacetate, [Rh-2(O2CCH3)(4)]
(1), and 2,6-diselenaspiro[3.3]heptane, Se2C5H8 (2), has
been solved ab
initio using laboratory source X-ray powder diffraction
(XRPD) data.
The rigid body refinement approach has been applied to
assist in
finding an adequate model and to reduce the number of
the refined
parameters. Complex [Rh-2(O2CCH3)(4).mu(2)Se(2)C(5)H(8)-Se,Se']
(3)
conforms to the triclinic unit cell with lattice parameters
of a =
8.1357(4), b = 8.7736(4), and c = 15.2183(8) Angstrom,
alpha =
77.417(3), beta = 88.837(3), and gamma = 69.276(4)degrees,
V =
989.66(8) Angstrom(3), and Z = 2. The centrosymmetric
P (1) over bar
space group was selected for calculations. The final values
of the
reduced wR(p), R-p, and chi(2) were calculated at 0.0579,
0.0433, and
5.95, respectively. The structure of 3 is a one-dimensional
zigzag
polymer built on axial Rh...Se interactions at 2.632(6)
Angstrom. The
2,6-diselenaspiro[3.3]heptane ligand acts as a bidentate
linker
bridging dirhodium units via both selenium atoms. The
geometrical
parameters of individual groups for rigid body refinement
have been
obtained from X-ray powder data for dirhodium(II) tetraacetate
(1) and
from single-crystal X-ray diffraction for diselenium molecule
2. The
crystal structures of 1 and 2 are reported here for the
first time. For
1 indexing based on XRPD data has resulted in the triclinic
unit cell P
(1) over bar with lattice parameters of a = 8.3392(7),
b = 5.2216(5),
and c = 7.5264(6) Angstrom, alpha = 95.547(10), beta =
78.101(6), and
gamma = 104.714(13)degrees, V = 309.51(5) Angstrom(3),
and Z = 1. The
final values were wR(p) = 0.0452, R-p = 0.0340, and chi(2)
= 1.99. The
1D polymeric motif built on axial Rh...O interactions
of the
centrosymmetric dirhodium units has been confirmed for
the solid-state
structure of 1. Compound 2,6-diselenaspiro[3.3]heptane
(2) conforms to
the monoclinic space group P2(1)/c with the unit cell
parameters of a =
5.9123(4), b = 19.6400(13), and c = 5.8877(4) Angstrom,
beta =
108.5500(10)degrees, V = 648.15(8) Angstrom(3), and Z
= 4.
2004-84 ????
Harvey, HG Slater, B Attfield, MP
Rational design of the pore system within the framework aluminium
alkylenediphosphonate series
CHEMISTRY-A EUROPEAN JOURNAL 10, 2004, 3270-3278.
We report here on the solvothermal synthesis and crystal structure
of
the hybrid organic-inorganic framework material
Al-2[O3PC3H6PO3](H2O),F-2.H2O (orthorhombic, Pmmn, a =
12.0591(2)
Angstrom, b = 19.1647(5) Angstrom, c = 4.91142(7) Angstrom,
Z = 4), the
second member of the Al-2[O3PCnH2nPO3](H2O)(2)F-2.H2O
series. The
structure consists of corrugated chains of corner-sharing
AlO4F2
octahedra in which alternating AlO4F2 octahedra contain
two fluorine
atoms in a trans or a cis configuration. The diphosphonate
groups link
the chains together through Al-O-P-O-Al bridges and through
the
propylene groups to form a three-dimensional framework
structure
containing a one-dimensional channel system. The linkage
of the
corrugated inorganic Al-O-P layers within the structure
results in the
formation of two types of channel that differ in size,
shape and
composition. The smaller channel is unoccupied; the larger
channel is
more elongated and contains two extra-framework water
molecules per
unit cell. A computational investigation into the driving
force that
controls the stacking arrangement of the Al-O-P inorganic
layers within
this series of compounds reveals that the stacking is
found to be
controlled by thermodynamic factors, arising chiefly from
the
conformation of the organic linker molecule used to connect
the
inorganic sheets. It is found that the registration of
the inorganic
layers can be engineered by selecting an appropriate,
simple organic
spacer or linker alkyl chain, where an even number of
carbon atoms in
the alkyl chain directs formation of aligned, stacked,
inorganic sheets
(AAAAAA), and an odd number directs formation of unaligned,
stacked
sheets (ABABAB) and the formation of one or two channel
types in the
resultant structure, respectively. This combination of
alkyl-chain
linkers in conjunction with corrugated inorganic layers
is an effective
tool to rationally design the pore system of hybrid framework
materials.
2004-85
Yang, Z Chen, XL Liang, JK He, M
Chen, JR
The crystal structure of alpha-SrGaBO4
CRYSTAL RESEARCH AND TECHNOLOGY 39, 2004, 634-642.
A new compound alpha-SrGaBO4 has been synthesized by solid state
reaction at high temperatures, and its structure has been
solved by
direct methods from powder X-ray diffraction. alpha-SrGaBO4
has an
orthorhombic system, Pccn space group, with lattice parameters
a =
15.3154(7) Angstrom, b = 8.9186(4) Angstrom, c = 5.8130(3)
Angstrom,
and Z = 8. The structure consists of infinite chains run
parallel to
the c axis and built up of GaO4 tetrahedral and BO3 triangles.
The
basic unit of these chains is a six - membered Ga2BO8
ring formed by
two GaO4 tetrahedra and one BO3 triangles. The Sr atom
is bonded to
eight oxygen atoms. The strontium atoms serve to hold
the chains
together through co-ordination with oxygen atoms. DTA
curve of
noncrystalline glassy SrGaBO4 was discussed. The XRD results
show no
phase transition occurs between -173degreesC and 127degreesC.
2004-86
Azuma, M Yoshida, H Saito, T Yamada,
T Takano, M
Pressure-induced buckling of spin ladder in SrCU2O3
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126, 2004, 8244-8246.
Pressure-induced structural phase transition of spin ladder compound
SrCu2O3 was investigated by synchrotron X-ray powder diffraction
with a
diamond anvil cell (DAC). The change was characterized
by a buckling of
the Cu2O3 plane in the rung direction of the ladder. The
structure of
the high-pressure phase was found to be essentially the
same as that of
CaCu2O3. Application of an external pressure of 3.4 GPa
therefore
affected the structure in the same manner that the chemical
(internal)
pressure does.
2004-87
Baranska, M Lasocha, W Kozlowski, H
Proniewicz, LM
New solid state Ni(II)-famotidine square-planar complex: powder
diffraction and spectroscopic studies
JOURNAL OF INORGANIC BIOCHEMISTRY 98, 2004, 995-1001.
Recent potentiometric studies have claimed that Ni(II) forms three
pH-dependent complexes with famotidine. We isolated two
of them from
the solution; namely the paramagnetic complex NiL with
octahedral
geometry and the diamagnetic complex NiH-L-2 with square-planar
geometry, The latter compound constitutes the subject
of this work. The
crystal structure of nickel (II) famotidine complex NiC8N7O2S3H13
discussed here, determined with the powder diffraction
method, has
shown that it belongs to a Pben space group (60) with
a, b, c =
24.328(4), 14.747(2), 7.786(1), V = 2793.6(5) Angstrom
3. R-F and R-wp
are 16.1% and 15.5%, respectively. Additionally, the UV-VIS,
FT-FIR and
Raman spectroscopic methods were employed to discuss and
support the
structure of the NiH-L-2 complex suggested by X-ray data.
The structure
presented in this work is the second example of the complex
of a
famotidine ligand with a transition metal ion in the solid
state. The
other one, reported from a single crystal X-ray structure
of famotidine
complex with Cu(II), is quite different.
2004-88
Lin, JH Sheptyakov, D Wang, YX Allenspach,
P
Structures and phase transition of vaterite-type rare earth
orthoborates: A neutron diffraction study
CHEMISTRY OF MATERIALS 16, 2004, 2418-2424.
The structure of vaterite-type rare earth orthoborate (LnBO(3)) has
long been a subject of interest and controversy. In the
:present work,
the crystal structures of two polymorphs of the vaterite-type
rare
earth orthoborates, i.e., the low- and high-temperature
modifications
of (Y0.92Er0.08)BO3, were solved and refined from neutron
powder
diffraction data. The low-temperature polymorph crystallizes
in a
C-centered monoclinic cell with C2/c space symmetry, the
unit cell
parameters being alpha = 11.3138(3) Angstrom, b = 6.5403(2)
Angstrom, c
= 9.5499(2) Angstrom, and beta = 112.902(1)degrees. The
boron atoms in
the structure are all tetrahedrally coordinated and form
the
three-membered ring borate B3O9 groups. The high-temperature
form
crystallizes in a new structure type in a monoclinic cell
with C2/c
space symmetry, and the unit cell constants alpha = 12.2019(3)
Angstrom, b = 7.0671(2) Angstrom, c = 9.3424(2) Angstrom,
and beta =
115.347(1)degrees. The borate groups in the high-temperature
structure
are all isolated flat BO3 triangles. As far as the structural
chemistry
is concerned, both structures are different from the typical
CaCO3
vaterite. However, they do share some common features,
particularly the
packing fashion of the cations, which results in similarly
looking
X-ray diffraction patterns as that of the typical vaterite.
2004-89
Veith, GM Lobanov, MV Emge, TJ Greenblatt,
M Croft, M
Stowasser, F Hadermann, J Van
Tendeloo, G
Synthesis and characterization of the new Ln(2)FeMoO(7) (Ln = Y, Dy,
Ho) compounds
JOURNAL OF MATERIALS CHEMISTRY 14, 2004, 1623-1630.
The new compounds Ln(2)FeMoO(7) (Ln = Y, Dy, Ho) have been synthesized
by solid-state reaction in evacuated silica tubes. The
crystal
structure of Dy2FeMoO7 and Ho2FeMoO7 was determined ab
initio by
simulated annealing in the R(3) over bar space group.
Transmission
electron microscopy study of Y2FeMoO7 revealed an unusual
lamellar
microstructure, composed of blocks with the structure
of different
zirconolite polymorphs. The dominant form corresponds
to the
zirconolite-2M type structure ( space group C2/c) with
a partially
ordered array of Fe and Mo ions. X-Ray near edge spectroscopy
data are
consistent with formally Fe3+ and Mo5+ oxidation states
for all
compounds. Magnetic and transport measurements are reported.
2004-90
Opozda, EM Lasocha, W Wlodarczyk-Gajda, B
Synthesis and characterization of some unsymmetrical Schiff base
ligands and their nickel(II) complexes incorporating o-phenylenediimine
units
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 630, 2004, 597-603.
Six new nickel(II) complexes of the unsymmetrical Schiff base ligands
derived from o-phenylenediamne were synthesized. These
complexes were
prepared by template and non-template reactions of the
precursor
3-acetyl-4-[N-(2'-aminophenyl)-amino]-3-buten-2-one (HLdegrees)
with
appropriate o-hydroxycarbonyl aromatic compounds, aromatic
1,3-oxo
aldehydes and 1,3-diketones. The nickel(II) compounds
were
characterized by analytical and spectroscopic methods.
Crystal
structure of complex
[3-acetyl-(6,7)-benzo-8-salicylidene-5,8-diazahepta-3-ene-2-onato(2-)]ni
ckel(II) (NiL1) has been determined by X-ray powder diffraction
method,
revealed that the molecules are almost flat, and there
are no forces
other than van der Waals interactions between molecules.
The structure
was solved by global optimisation technique and refined
by the Rietveld
method, obtained R-F and R-wp are 11.6 and 17.4%, respectively.
The
synthesis of a new unsymmetrical nickel(II) tetraazamacrocyclic
complex
is also described.
2004-91
Bostrom, M Gemmi, M Schnelle, W
Eriksson, L
Synthesis, properties and structure determination of
Nb2O3(SO4)(2) . (1)/4H2O from neutron and synchrotron
X-ray
powder diffraction data
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 1738-1745.
The blue diamagnetic compound Nb2O3(SO4)(2) (.) 1/4H(2)O was
synthesized by the reaction of niobium metal and boiling
sulfuric acid.
The unit cell was deduced from electron diffraction patterns
and the
crystal structure was solved from X-ray powder diffraction
data and
refined from combined X-ray synchrotron and neutron powder
diffraction
data. Nb2O3(SO4)(2) (.) 1/4H(2)O crystallizes in the space
group R-3
(148) with the cell parameters a = 10.384(2) Angstrom
and c = 26.55(2)
Angstrom in the hexagonal setting. The structure features
covalently
bonded sulfate tetrahedra and niobate octahedra.
2004-92 ?????
Anokhina, EV Jacobson, AJ
[Ni2O(L-Asp)(H2O)(2)] . 4H(2)O: A homochiral 1D helical chain
hybrid compound with extended Ni-O-Ni bonding
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126, 2004, 3944-3045.
2004-93
Jurgens, B Irran, E Hoppe, HA Schnick,
W
Phase transition of a dicyanamide with rutile-like structure: Syntheses
and crystal structures of alpha- and beta-Cd[N(CN)(2)](2)
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 630, 2004, 219-223.
Cadmium dicyanamide Cd[N(CN)(2)](2) was synthesized through aqueous
ion
exchange at room temperature. A reversible phase transition
was
detected by in situ X-ray powder diffractometry above
55 degreesC. The
crystal structures of both phases were determined by X-ray
powder
diffraction (beta-Cd[N(CN)(2)](2): T = 22 degreesC, a
= 621.60(3), b =
748.76(4), c = 770.21(5) pm, beta = 91.784(3)degrees,
P2(1)/n (no. 14),
Z = 2, wR(p) = 0.063, R-p = 0.050, R-F = 0.059; alpha-Cd[N(CN)(2)](2):
T = 150 degreesC, a = 624.62(5), b = 752.92(6), c = 768.30(7)
pm, Pnnm
(no. 58), Z = 2, wR(p) = 0.083, R-p = 0.064, R-F = 0.087).
Both
polymorphs consist of Cd2+ and bent planar [N(CN)(2)](-)
ions.
alpha-Cd[N(CN)(2)](2) crystallizes analogously to rutile
and is
isotypic with M-II[N(CN)(2)](2) (M = Mg, Cr, Mn, Co, Ni,
Cu). The
monoclinic low-temperature polymorph beta-Cd[N(CN)(2)](2)
is closely
related to that of the orthorhombic high-temperature polymorph
alpha-Cd[N(CN)(2)](2) by a translationengleiche transition
of index 2.
2004-94
Cremer, U Ruschewitz, U
NaCu5(C-2)(3): The first alkali metal transition metal acetylide with
a
three-dimensional framework structure
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 630, 2004, 161-166.
By heating the red residue of the reaction of NaC2H and CuI in liquid
ammonia at 463 K for 30 min in a dynamic vacuum orange
polycrystalline
NaCu5(C-2)(3) is obtained. The crystal structure was solved
and refined
from X-ray powder diffraction data (orthorhombic, Puma,
a 732.80(2) pm,
b = 1099.63(4) pm, c = 726.15(2) pm, Z = 4 R-B = 0.030).
It consists of
a three-dimensional framework of Cu-I and C-2(2-) ions
with small
channels running parallel to [100] and [001]. The sodium
ions reside at
the inter-sections of these channels. The vibrational
spectra of
NaCu5(C-2)(3) show some similarities with the spectra
of
phenylethynylcopper(I), but they are different to those
Of Cu2C2.
Therefore NaCu5(C-2)(3) does probably not represent a
crystalline model
compound for the unknown structure of amorphous Cu2C2.
2004-95
Hostettler, M Schwarzenbach, D Helbing, J
Dmitriev, V Weber, HP
Structure and SHG of the high pressure phase IV of HgBr2
SOLID STATE COMMUNICATIONS 129, 2004, 359-363.
Angle dispersive X-ray diffraction experiments on mercuric bromide
(HgBr2) under high pressure up to 11.0 GPa were carried
out at room
temperature using synchrotron radiation. In addition to
the already
known four different phases of HgBr2 in the pressure-temperature
range
of p < 4.5 GPa, 90 < T < 600 K Our observations
show the existence of a
new phase (V) above 9.0 GPa and, together with published
material,
support the phase transition sequence: (I) orthorhombic-(II)
orthorhombic-(III) monoclinic-(IV) trigonal-(V) trigonal/hexagonal.
The
structure of phase IV with space group symmetry P3 has
been determined
from powder diffraction data. The observation of
second-harmonic-generation signals confirms the absence
of an inversion
center. The structure of phase IV is a commensurately
modulated variant
of the CdI2 type layer structure, where part of the Hg
atoms are
displaced from the centers of the HgBr6 octahedra by a
much as 0.76
Angstrom in the direction perpendicular to the layers.
2004-96
Harvey, HG Attfield, MP
Synthesis, crystal structures, and properties of novel lamellar gallium
methylenediphosphonates
CHEMISTRY OF MATERIALS 16, 2004, 199-209.
Three new gallium methylenediphosphonates:
(C5H5NH)[Ga-2(H2O)(2)(O3PCH2PO3)(O3PCH2-PO3H)] (1) (monoclinic,
P2(1)/c, a = 11.0848(2) Angstrom, b = 8.4441(2) Angstrom,
c = 9.4419(1)
Angstrom, beta = 104.537(1)degrees, Z = 2),
[(CH3)(4)N][Ga-2(H2O)(2)(O3PCH2PO)(O3PCH2PO3H)] (2) (monoclinic,
C2/c,
a = 22.1628(8) Angstrom, b = 8.5724(2) Angstrom, c = 9.4455(2)
Angstrom, beta = 95.486(3)degrees, Z = 4), and
(C5H5NH)[Ga(H2O)(O3PCH2PO3)] (3) (monoclinic, P2(1)/a,
a = 9.5721(7)
Angstrom, b = 8.6140(6) Angstrom, c = 12.894(1) Angstrom,beta
=
99.961(3)degrees, Z = 4) have been synthesized by solvothermal
methods
in the presence of organocations, and their structures
were determined
using powder (1 and 2) and single-crystal X-ray diffraction
data (3).
All three materials contain a novel corrugated [Ga(H2O)(O3PCH2PO3)](-)
layer motif composed of octahedral GaO5(OH2) units that
are linked
together by the diphosphonate groups. One of the oxygen
atoms of each
diphosphonate group protrudes into the interlamellar region
where it
hydrogen bonds to adjacent layers in 1 and 2 to form hydrogen-bonded
framework structures, or to the pyridinium. cations in
the lamellar
material 3. The stacking arrangement of the layers in
1 and 2 is shown
to be dependent on the organocations present during the
synthesis, and
to form materials with one- or two-types of hydrogen-bonded
channels,
respectively. Material 3 is an intermediate phase isolatable
during
formation of 1 and is convertible to the type of hydrogen-bonded
framework of 1 by solvothermal, thermal, or solution ion-exchange
methods.
2004-97
Nunes, C
Suryanarayanan, R Botez, CE Stephens,
PW
Characterization and crystal structure of D-mannitol hemihydrate
JOURNAL OF PHARMACEUTICAL SCIENCES 93, 2004, 2800-2809.
The objectives of this study were (i) to isolate and characterize
mannitol hydrate, and (ii) to solve its crystal structure
from
high-resolution synchrotron X-ray powder diffraction data.
Mannitol
hydrate was prepared by freeze-drying aqueous mannitol
solutions (5%
w/v) under controlled conditions. X-ray powder diffractometry,
differential scanning calorimetry, and thermogravimetric
analyses
indicated that mannitol exists as a hemihydrate (C6H14O6
. 0.5H(2)O).
Synchrotron data were collected on the X3B1 beamline at
the National
Synchrotron Light Source. The simulated annealing program
PSSP was used
to solve the structure, which was subsequently refined
by Rietveld
analysis using the program package GSAS. The compound
crystallizes in
space group P1, with alpha=9.8963 Angstrom, b=10.5424
Angstrom,
c=4.7860 Angstrom, alpha=102.589degrees, beta = 86.092degrees,
and
gamma =116.079degrees. The unit cell contains two dissimilar
D-mannitol
molecules and one water molecule, forming a hydrogen bonding
pattern
significantly different from that seen in the anhydrous
polymorphs.
2004-98
Dinnebier, R Sofina, N Jansen, M
The structure of the high temperature modification of lithium triflate
(gamma-LiSo(3)CF(3))
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 630, 2004, 1613-1616.
The high temperature modification of lithium triflate (gamma-LiSO3CF3)
crystallises in the orthorhombic space group Cmca with
the lattice
parameters a = 6.3022(4), b = 8.6989(5), and c 20.1262(14)
Angstrom
(synchrotron powder diffraction data, T 456 K). The crystal
structure
of gamma-LiSO3CF3 is disordered, in the cationic as well
as the anionic
partial structure, and exhibits double layers of triflate
anions with
the lipophilic CF3-groups facing each other. The lithium
ions could not
be located by the diffraction experiment due to their
high mobility.
The staggered triflate anion is twofold disorderd leading
to two
different positions on top of each other which are tilted
to one
another.
2004-99 ???
Zanardi, S Alberti, A Cruciani, G
Corma, A Fornes, V Brunelli, M
Crystal structure determination of zeolite Nu-6(2) and its layered
precursor Nu-6(1)
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 43, 2004, 4933-4937.
2004-100
Kirik, SD Mulagaleev, RF Blokhin, AI
[Pd(CH3COO)(2)](n) from X-ray powder diff raction data
ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS 60,
2004, M449-M450.
The water-insoluble title compound,
catena-poly[palladium(II)-di-mu-acetato-kappa(4)O:O'],
[Pd(C2H3O2)(2)](n), was obtained from a nitratopalladium
solution and
acetic acid as a pale-pink powder. Ab initio crystal structure
determination was carried out using X-ray powder diffraction
techniques. Patterson and Fourier syntheses were used
for atom location
and the Rietveld technique was applied for the final structure
refinement. The structure consists of palladium acetate
complexes
connected into polymeric chains running along b, in which
two Pd atoms
are bridged by two acetate groups that are in a cis configuration
with
respect to one another. The unique Pd atom lies on a site
with 2/m
symmetry and the acetate moieties have imposed m symmetry;
these are
joined into infinite chains running along the b direction.
The shortest
Pd...Pd distance in the row is 2.9192 (1) Angstrom. The
planes of
adjacent palladium complexes are inclined towards each
other, the angle
between the planes being approximately 30degrees.
2004-101
Muhle, C Nuss, J Dinnebier, RE Jansen,
M
On potassium tetracyanoplatinate(II), potassium
tetracyanopalladate(II), and their monohydrates
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 630, 2004, 1462-1468.
We have determined the crystal structures of the potassium
tetracyanoplatinates(II) and -palladates(II), and of their
monohydrates, by X-ray powder diffraction techniques and
single crystal
structure analysis. K-2[Pt(CN)(4)]: orthorhombic; Pccn;
a = 1370.11(2);
b = 907.09(1); c = 703.91(2) pm; Z = 4; R-F(2) = 0.0903
(N(hkl) = 415).
K-2[Pt(CN)(4)] . H2O: orthorhombic; Pnna; a = 715.79(4);
b = 977.91(6);
c = 1322.46(8) pm; Z = 4; R(F)(N') = 0.027 (N'(hkl) =
1066).
K-2[Pd(CN)(4)]: monoclinic; P2(1)/c; a = 433.03(2); b
= 782.90(3); c =
1328.17(6) pm; beta = 93.069(3)degrees; Z = 2; R-p = 0.0583
(N(hkl) =
352). K-2[Pd(CN)(4)] . H2O: orthorhombic; Pnna; a = 721.48(6);
b =
976.77(8); c = 1326.4(1) pm; Z = 4; R(F)(N') = 0.048 (N'(hkl)
= 1137).
In all examined representatives the anions are stacked
one upon the
other, even though they are tilted in part. The results
are completed
by spectroscopic and thermo analytical investigations.
2004-102
Ei-Himri, A Marrero-Lopez, D Nunez, P
TI Pt2Mo3N and PdPtMo3N: new interstitial nitrides prepared from
freeze-dried precursors
SO JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 3219-3223.
AB The molybdenum bimetallic and trimetallic nitrides Pt2Mo3N and PdPtMo3N
have been synthesized by ammonolysis of the stoichiometric
amorphous
precursor, obtained by freeze drying of aqueous solutions
of the
appropriate metal salts. These compounds have been characterized
by
elemental analysis, energy-dispersive analysis of X-rays,
X-ray
diffraction, scanning electron microscopy, transmission
electron
microscopy and thermogravimetry analysis under an oxygen
atmosphere.
Pt2Mo3N and PdPtMo3N crystallize in the cubic space group
P4(1)32
(213), with lattice parameters of a = 6.83586(4) and 6.82542(3)
Angstrom, respectively, and form with the unusual filled
beta-manganese
structure. These compounds are stable under air up to
580 K, the
oxidation being complete at 910K.
2004-103
Lobanov, MV Greenblatt, M Caspi, EN
Jorgensen, JD Sheptyakov, DV
Toby, BH Botez, CE Stephens, PW
Crystal and magnetic structure of the Ca3Mn2O7 Ruddlesden-Popper phase:
neutron and synchrotron x-ray diffraction study
JOURNAL OF PHYSICS-CONDENSED MATTER 16, 2004, 5339-5348.
The crystallographic and magnetic structures of Ca3Mn2O7
Ruddlesden-Popper phase have been determined by a combination
of
neutron and synchrotron x-ray diffraction. Two-phase behaviour
observed
at room temperature is attributed to an incomplete structural
phase
transition. The magnetic structure was solved in the Cm'c2'(1)
Shubnikov group with dominant G-type antiferromagnetic
order in the
perovskite bilayers. The temperature evolution of the
structural and
magnetic parameters is presented.
2004-104
Amami, M van Smaalen, S Salah, AB
Helluy, X Sebald, A
Structural investigation of trimethylammonium tetrachloromercurate
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 2961-2970.
The temperature dependence of the crystal structure of TrMA(2)HgCl(4)
(TrMA = trimethylammonium) is studied by single-crystal
and powder
X-ray diffraction between 161 and 373 K. Below room temperature,
we did
not find significant changes of the crystal structure.
The phase
transition at 325 K is described by a rotation of one
of the two
independent TrMA(+) cations by 40degrees around the N-H
axis, resulting
in major rearrangements in the network of hydrogen bonds.
A large
change of the volume of the unit cell is found at the
phase transition
at 357 K, resulting in damage to the single crystals.
Powder
diffraction then shows that this transition can be described
as a
alpha-beta transition between the alpha and beta-K2SeO4
structure
types. Structure refinements employing alternatively restrictions
by
the space group and additional restrictions by the C-3
non-crystallographic site symmetry for the TrMA(+) cations
show that
significant deviations from C-3 symmetry of the TrMA(+)
cations do not
exist at any temperature. The molecular dynamics and orientational
disorder were studied by the maximum entropy method applied
to the
X-ray data. The diffraction results are corroborated by
temperature
dependent NMR experiments.
2004-105 ???
Nyman, M Bonhomme, F Alam, TM Parise,
JB Vaughan, GMB
[SiNb12O40](16-) and [GeNb12O40](16-): Highly charged Keggin ions with
sticky surfaces
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 43, 2004, 2787-2792.
2004-106
Derollez, P Hernandez, O Hedoux, A
Guinet, Y Masson, O
Lefebvre, J Descamps, A
Structural and microstructural description of the glacial state in
triphenyl phosphite from powder synchrotron X-ray diffraction
data and
Raman scattering investigations
JOURNAL OF MOLECULAR STRUCTURE 694, 2004, 131-138.
The structure and microstructure (refinement of the isotropic size
and
microstrain parameters) of the glacial state in triphenyl
phosphite
(TPP, P(OC6H5)(3)) transformed at 222K have been determined
from powder
synchrotron X-ray diffraction data through a Rietveld
and a Le Bail
refinement, respectively. It is shown that the glacial
state is
composed of crystallites of the stable crystal phase coexisting
with
non-transformed supercooled liquid, the apparent size
of the
crystallites-depending on the aging temperature at which
the glacial
state is isothermally formed, [Phys. Rev. B 60 (1999)
9390]-being equal
to 329.2(2) Angstrom at 222K. The molecular conformation
is slightly
less mirror-symmetric than the one in the crystal state,
and
correlatively only one of the two unusual weak intermolecular
C-H...O
hydrogen bonds already observed in the latter state is
encountered in
the glacial one. Additional Raman scattering investigations
confirm the
previous result and reveal in addition that no hydrogen
bonding
interaction is observed neither in the glass nor in the
liquid states.
2004-107
Solovyov, LA Kim, TW Kleitz, F Terasaki,
O Ryoo, R
Comprehensive structure analysis of ordered carbon nanopipe materials
CMK-5 by X-ray diffraction and electron microscopy
CHEMISTRY OF MATERIALS 16, 2004, 2274-2281.
The structure of ordered mesoporous carbon materials CMK-5 was analyzed
in detail by transmission electron microscopy (TEM) and
X-ray
diffraction (XRD) analysis by applying the recently developed
continuous density function technique. The materials present
twodimensional (2-D) hexagonally ordered arrays of carbon
nanopipes
formed within the mesopores of SBA-15 silica templates
used for their
fabrication. The series of CMK-5 carbons were synthesized
by applying
the templates of different pore widths and two carbon
precursors:
furfuryl alcohol and acenaphthene. All the materials were
well-ordered,
exhibiting five distinct XRD reflections, high nitrogen
BET specific
surface areas (about 2500 m(2)/g), and large pore volumes
(about 2
cm(3)/g). TEM analysis and XRD modeling allowed precise
determination
of the mesostructure characteristics such as the nanopipe
diameter,
wall thickness, and shape. Around 15% of the space between
the
nanopipes was found to be occupied by carbon interconnections
formed
inside the complementary pores of the SBA-15 templates.
The structure
parameters determined correlated well with the synthesis
procedures and
were fully consistent with the nitrogen adsorption and
thermogravimetric data. The differences in the properties
and the
formation mechanisms of the materials synthesized by applying
furfuryl
alcohol and acenaphthene carbon precursors were analyzed
based on the
whole scope of data obtained.
2004-108
Meshi, L Talianker, M Munitz, A
Determination of the structure of UFe2Al10 compound
JOURNAL OF ALLOYS AND COMPOUNDS 370, 2004, 206-210.
The atomic structure of a new ternary phase UFe2Al10 appearing in the
U-Fe-Al system was determined using direct methods applied
to X-ray
powder diffraction data. High resolution electron microscopy
combined
with the methods of crystallographic image processing
was used for the
verification of the structural model. The UFe2Al10 phase
is
orthorhombic and belongs to Cmcm space group, its unit
cell contains 40
Al, eight Fe, and four U atoms. The lattice parameters
obtained after
Rietveld refinement are: a = 8.919 Angstrom, b = 10.208
Angstrom, and c
= 9.018 Angstrom. The reliability factors characterizing
the Rietveld
refinement procedure are: R-p = 5.9%, R-wp = 8.1%, and
R-b = 2.9%.
2004-109
Chen, XL He, M Xu, YP Li, HQ
Tu, QY
KCaF(CO3) from X-ray powder data 60, 2004, 150-151.
ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE
Potassium calcium fluoride carbonate, KCaF(CO3), has been synthesized
and its structure solved from X-ray powder diffraction
data. The K, Ca,
F and C atoms lie at sites with (6) over bar m2 imposed
symmetry and
the unique O atom has imposed mm site symmetry. The compound
consists
of Ca-F-Ca chains parallel to the c axis and planar CO3
groups
perpendicular to the c axis, the corners of the hexagonal
cell being
occupied by K+ ions. The compound is not a solid solution,
since the
structure differs from those of both KF and CaCO3.
2004-110
Cheung, EY Harris, KDM Johnston, RL
Kitchin, SJ
Hadden, KL Zakrzewski, M
Rationalizing the structural properties of bupivacaine base - A local
anesthetic - Directly from powder X-ray diffraction data
JOURNAL OF PHARMACEUTICAL SCIENCES 93, 2004, 667-674.
Bupivacaine belongs to a family of 1-alkyl-2',6'-pipecoloxylidides,
which has shown promise as reversible action potential
blockers that
can introduce prolonged local anesthetic effects. The
crystal structure
of the free-base form of bupivacaine has been determined
directly from
powder X-ray diffraction data using the Genetic Algorithm
technique for
structure solution, followed by Rietveld refinement. This
work further
emphasizes the scope and utility of ab initio structure
solution
directly from powder X-ray diffraction data for tackling
structural
problems within the biomedical field, leading to opportunities
for the
investigation of structure-property relationships.
2004-111
Gonzalez-Mendez, LM Cumbrera, FL Garcia-Cuesta,
MC Sanchez-Bajo, F
Ortiz, AL Higes-Rolando, FJ Luna-Giles,
F
Ab initio structural determination of
2-(2-pyridyl)imino-N-(2-thiazolin-2-yl)thiazolidine from
powder
diffraction data
MATERIALS LETTERS 58, 2004, 672-678.
Structural determination using X-ray powder diffraction is usually
restricted to relatively simple structures, although powder
diffraction
data are frequently used to refine, via the Rietveld method,
approximately known structures. In this work, the relatively
complex
crystalline structure of a compound of high pharmaceutical
interest
(C11H12N4S2) has been firstly ab initio determined from
its X-ray
powder diffraction pattern and subsequently refined by
the Rietveld
method. This refined structure is in excellent agreement
with that
obtained previously from single-crystal data. As a consequence
of the
severe overlapping between adjacent reflections, direct
methods failed,
whereas we obtained good outcomes with 'real space' methods.
This work
shows that within the current state-of-art (hardware,
software,
numerical methods, etc.), relatively complex structures
can be afforded
by means of powder diffraction.
2004-112
Hu, XR Yuan, ZQ Lu, GL
Determination of crystal structures of polymorphic chlorothalonil using
Monte Carlo simulated annealing and Rietveld refinement
POWDER DIFFRACTION 19, 2004, 325-328.
Crystal structures of types II and III chlorothalonil,
2,4,5,6-tetrachloro-1,3-dicyanobenzene, (C8Cl4N2) were
solved by
applying Monte Carlo simulated annealing techniques to
X-ray powder
diffraction data and refined using the Rietveld method.
Both types of
chlorothalonil crystallize in monoclinic symmetry (space
group P2(1)
and two molecules per unit cell). Lattice parameters are:
a=8.1615(18)
Angstrom, b=9.4191(19) Angstrom, c=6.4728(14) Angstrom,
beta=93.7307(64)degrees and V=497.8 Angstrom(3) for type
II, and
a=8.6003(10) Angstrom, b=9.2382(11) Angstrom, c=6.3024(7)
Angstrom,
beta=96.2152(60)degrees and V=498.5 Angstrom(3) for type
III. The
structures of both types of chlorothalonil are stacked
by two coplanar
molecular sheets paralleled to the b-axis. The adjacent
two paralleled
molecules in type II are on the same plane, while those
in type III are
on two different parallel planes.
2004-113
Dikarev, EV Chernyshev, VV Shpanchenko, RV
Filatov, AS Petrukhina, MA
Bulk material vs. single crystal: powder diffraction to the rescue
DALTON TRANSACTIONS iss 24, 2004, 4120-4123.
The crystal structure of bulk microcrystalline material obtained by
interaction of two rigid building blocks, namely dirhodium(II)
tetra(trifluoroacetate), [Rh-2(O2CCF3)(4)], and bis(4'-pyridyl)
diphenylsilane, (C6H5)(2)Si(C5H4N)(2), has been solved
ab initio using
X-ray powder diffraction data. The title product of the
1:1
composition, [Rh-2(O2CCF3)(4).(mu(2)-(C6H5)(2)Si(C5H4N)(2))],
is a
one-dimensional zigzag polymer built on axial Rh...N interactions
averaged at 2.16 Angstrom. Its structural characterization
complements
the previously reported product of the 2:1 composition
obtained from
the same reaction, namely
{[Rh-2(O2CCF3)(4)](2).(mu(4)-(C6H5)(2)Si(C5H4N)(2))}.
The latter has a
2D layered network revealed by the single crystal diffraction
study. A
combination of powder and single crystal X-ray techniques
is shown to
be methodologically important and complementary for understanding
of
product assembling in the system.
2004-114
Evans, IR Howard, JAK Szecsenyi, KM
Leovac, VM Jacimovic, ZK
Synthesis, characterization and crystal structure of a novel Ni(II)
complex, Ni(L-H)(2) (L=3,5-dimethyl-1-thiocarboxamidopyrazole)
JOURNAL OF COORDINATION CHEMISTRY 57, 2004, 469-476.
A new complex, Ni(L-H)(2), L = 3,5-dimethyl-1-thiocarboxamidopyrazole,
has been synthesized and characterized by IR spectroscopy,
magnetic and
electrical measurements. Its crystal structure was solved
from powder
X-ray diffraction data. The compound crystallizes in space
group P (1)
over bar with two independent half-molecules containing
Ni(II)
coordinated by four nitrogen atoms in a square-plane.
The packing
pattern consists of two stacks of parallel molecules mutually
tilted at
an angle of 118degrees.
2004-115 ???
Rubin-Preminger, JM Bernstein, J Harris, RK
Evans, IR Ghi, PY
Variable temperature studies of a polymorphic system comprising two
pairs of enantiotropically related forms: [S,S]-ethambutol
dihydrochloride
CRYSTAL GROWTH & DESIGN 4, 2004, 431-439.
Of the four known polymorphs of [S,S] -ethambutol dihydrochloride,
two
transform in an enantiotropic single-crystal-to-single-crystaI
phase
transformation from Form II to Form I on heating. The
crystal
structures of these two forms have been solved and compared.
Because
the other two forms are metastable and are only obtained
from the melt,
single-crystal data could not be obtained on them. However,
all four
forms have been characterized, and their relative thermodynamic
relationships have been investigated by variable-temperature
solid-state C-13 NMR, variable-temperature powder X-ray
diffraction
studies, differential scanning calorimetry, and optical
microscopy.
2004-116
Money, VA Evans, IR Elhaik, J Halcrow,
MA Howard, JAK
An X-ray powder diffraction study of the spin-crossover transition
and
structure of bis (2,6-dipyrazol-1-ylpyrazine)iron(II)
perchlorate
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 60, 2004, 41-45.
The crystal structure of the iron(II) spin-crossover compound
[Fe(C10H8N6)(2)](ClO4)(2) in the high-spin state has been
solved from
powder X-ray diffraction data using the DASH program and
refined using
Rietveld refinement. The thermal spin transition has been
monitored by
following the change in unit-cell parameters with temperature.
The
title compound has been found to undergo a crystallographic
phase
change, involving a doubling of the crystallographic a
axis, on
undergoing the spin transition.
2004-117
Mahe, N Bataille, T
Synthesis, crystal structure from single-crystal and powder x-ray
diffraction data, and thermal behavior of mixed potassium
lanthanide
squarates: Thermal transformations of layered
[Ln(H2O)(6)]K(H2C4O4)(C4O4)(2) into pillared LnK(C4O4)2
(Ln = Y, La,
Gd, Er)
INORGANIC CHEMISTRY 43, 2004, 8379-8386.
A new series of mixed potassium and rare-earth squarates,
[Ln(H2O)(6)]K(H2C4O4)(C4O4)(2) (Ln = Y, La, Gd, Er), has
been
synthesized and structurally characterized from single-crystal
X-ray
diffraction and spectroscopic analyses. The yttrium-based
compound
crystallizes with a monoclinic symmetry, space group C2/c
[a =
8.3341(2) Angstrom, b = 37.7094(g) Angstrom, c = 11.7195(3)
Angstrom,
beta = 90.3959(9)degrees, V = 3683.1(2) Angstrom(3), Z
= 8]. The
structure is built from layers maintained together via
hydrogen bonds.
Within a layer, squarate ligands act as linkers between
lanthanide and
potassium cations. The thermal decomposition of the precursors
has been
studied by powder thermodiffractometry and thermal analyses.
It is
shown that crystalline intermediate phases are formed
during the
degradation. Among them, unprecedented mixed anhydrous
squarates,
LnK(C4O4)(2), could be isolated. The crystal structure
of the Y
compound has been solved ab initio from X-ray powder diffraction
data,
using direct-space methods [a = 6.2010(5) Angstrom, c
= 11.639(l)
Angstrom, V = 447.55 Angstrom(3), Z = 2]. The structure
consists of
layers of edge-sharing YO8 and KO8 antiprisms, pillared
by
mu(8)-squarate groups. The end of the precursor decomposition
is marked
by the formation of cubic sesquioxides Ln(2)O(3), including
lanthanum
oxide.
2004-118
Degtyareva, O McMahon, MI Nelmes, RJ
Pressure-induced incommensurate-to-incommensurate phase transition
in
antimony
PHYSICAL REVIEW B 70, 2004, 184119.
An incommensurate composite phase with a monoclinic host-guest
structure, designated Sb-IV, is found between the previously
known Sb-I
and Sb-II phases, and an incommensurate to incommensurate
transition
between phases II and IV is described. The monoclinic
Sb-IV phase is
observed on both pressure increase between 8.2 and 9.0
GPa and on
pressure decrease between 8.0 and 6.9 GPa. The full structure
of Sb-IV,
including a determination of the structural modulations
of the host and
guest components, is reported from x-ray powder diffraction
data. The
high-pressure phase of arsenic, As-III, is shown to have
the same
monoclinic composite structure.
2004-119
Dacheux, N Clavier, N Robisson, AC
Terra, O
Audubert, F Lartigue, JE Guy,
C
Immobilisation of actinides in phosphate matrices
COMPTES RENDUS CHIMIE 7, 2004, 1141-1152.
In the field of the immobilisation of high-activity-level and long-life
radwaste (HAVL) for a deep underground repository, several
phosphate
matrices were already proposed as good candidates to delay
the release
of actinides in the near-field of such disposal. Among
them, thorium
phosphate-diphosphate (TPD), monazites/brabantites, britholites,
and
TPD/monazite composites were extensively studied. The
synthesis of
samples doped with actinides (Th, U...) through wet and
dry chemistry
methods then their complete characterisation are reported.
Their
chemical durability is also examined. These materials
appear as
promising matrices to immobilise tetravalent and/or trivalent
actinides.
2004-120
Brandel, V Dacheux, N
Chemistry of tetravalent actinide phosphates - Part I
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 4743-4754.
actinide (IV) phosphate; phosphates of tetravalent cations; thorium
phosphate; uranium phosphate; neptunium phosphate; plutonium
phosphate;
protactinium phosphate
The chemistry and crystal structure of phosphates of tetravalent
cations, including that of actinides was reviewed several
times up to
1985. Later, new compounds were synthesized and characterized.
In more
recent studies, it was found that some of previously reported
phases,
especially those of thorium, uranium and neptunium, were
wrongly
identified. In the light of these new facts an update
review and
classification of the tetravalent actinide phosphates
is proposed in
the two parts of this paper. Their crystal structure and
some chemical
properties are also compared to non-actinide cation phosphates.
2004-121
Martinez-Garcia, R Reguera, E Rodriguez, J
Balmaseda, J Roque, J
Crystal structures of some manganese(II) and cadmium hexacyanoferrates
(II,III) and structural transformations related to the
sorption of
Cesium
POWDER DIFFRACTION 19, 2004, 255-264.
Mn2+ and Cd2+ form a family of isostructural hexacyanoferrates(II,III).
Their crystal structures, including those of mixed compositions
containing K+ and Cs+ as charge balance cations, were
resolved and
refined from XRD powder patterns. The crystal structures
of
M-3[Fe(CN)(6)](2) . xH(2)O and MCs2[Fe(CN)(6)] (where
M=Mn, Cd)
were refined in the space group Fm3m. The mixed salts,
MK2[Fe(CN)(6)] . (2)H(2)O, were found to be orthorhombic
(space
group Pmn2(1)). The orthorhombic structure results from
a local
distortion due to monohydrated potassium ions located
in interstitial
sites. On ionic exchange in an aqueous solution containing
Cs+, the
orthorhombic distortion disappears and the cubic cell
is obtained. Cs+
is a large ion, which practically fills the available
interstitial
voids stabilizing the cubic structure. In solutions of
K+ and Cs+ the
single salts, M-2[Fe(CN)(6)] . 8H(2)O (monoclinic
P2(1)/n) also
transform, in this case liberating M2+ ions and forming
the
corresponding mixed salts. An analogous but slow structural
transformation was also observed in the anhydrous forms
of these single
salts. These structural transformations could be relevant
to the use of
these compounds as ion exchangers and particularly for
the sorption of
Cs-137(+) from radioactive waste solutions. The XRD data
were
complemented with structural information from infrared
(IR), Mossbauer
and water vapor adsorption techniques.
2004-122
Martinez-Garcia, R Reguera, E Balmaseda, J
Ramos, G Yee-Madeira, H
On the crystal structures of some nickel hexacyanoferrates (II,III)
POWDER DIFFRACTION 19, 2004, 284-291.
The crystal structures of some nickel hexacyanoferrates (II, III),
including mixed compositions containing Na+, K+ and Cs+,
were resolved
and refined from XRD powder patterns. Data from infrared,
Mossbauer and
adsorption techniques provided complementary structural
information.
The crystal structures of Ni-3[Fe(CN)(6)](2) . 16H(2)O
and
NiCS2[Fe(CN)(6)] were refined in space group Fm3m.
NiNa2[Fe(CN)(6)] . 2H(2)O and NiK2[Fe(CN)(6)] .
2H(2)O
were found to be orthorhombic (space group Pmn2(1)). This
structure
(Pmn21) results from a distortion around the alkali ion,
which appears
as a monohydrated interstitial species. On ionic exchange
in an aqueous
solution containing Cs+, the orthorhombic distortion disappears
and the
cubic cell is obtained. Cs+ is a large cation and space
is not
available for interstitial water molecules. This orthorhombic
model is
also supported by the Mossbauer spectra of the ferrous
analogs,
FeK2[Fe(CN)(6)] . xH(2)O and Fe[Pt(CN)(6)].
2004-123
Heymann, G Beyer, K Huppertz, H
High-temperature synthesis, crystal structure, and properties of the
new sodium rare-earth oxide borates Na2RE2(BO3)(2)O (RE
= Dy, Ho)
ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES
59, 2004, 1200-1208.
The new monoclinic oxide borates Na2RE2(BO3)(2)O (RE = Dy, Ho) were
synthesized using standard solid-state reactions in the
temperature
range 900-950 degreesC. They are isotypic to the known
phases
Na2RE2(BO3)(2)O (RE = Y, La, Nd, Sm-Gd, Er). The single
crystal X-ray
structure determination of Na2Dy2(BO3)(2)O revealed: P2(1)/c,
a
1063.9(l), b = 626.2(l), c = 1025.3(1) pm, beta = 117.76(1)degrees,
Z =
4, Rl = 0.0221, wR2 = 0.0402 (all data). The corresponding
lattice
parameters of Na2HO2(BO3)(2)O determined from powder data
are a =
1061.2(5), b = 623.7(2), c = 1022.5(3) pm, and 0 = 117.7(1)degrees.
The
structure consists of infinite sheets of REO8-polyhedra
in the
bc-plane, which are seperated by sodium atoms. The BO3-groups
are
isolated forming layers in the bc-plane. The results of
IR-
spectroscopic investigations, temperature-resolved in-situ
powder-diffraction measurements, and DTA/TG measurements
on
Na2Dy2(BO3)20 are also presented.
2004-124
Ardizzoia, GA Brenna, S Castelli, F
Galli, S
LaMonica, G Masciocchi, N Maspero,
A
Metal imidazolato polymers: synthesis, characterization and crystal
structure of new silver(I) triphenylphosphine derivatives
POLYHEDRON 23, 2004, 3063-3068.
When the polymeric complex [Ag(im)](n) (Him = imidazole) is reacted
with PPh3 (PPh3 = triphenylphosphine), it yields the
[Ag-2(mu(2)-im)(2)(PPh3)(3)] and [Ag(mu(2)-im)(PPh3)(2)](n)
species,
shown to contain wavy chains of metal ions, singly bridged
by
N,N'-exobidentate imidazolate ligands. The former, crystallised
as the
CH2Cl2 solvate, contains two non-equivalent silver(I)
ions, differing
in the number of coordinated phosphines (one, in trigonal
planar
stereochemistry, or two, having tetrahedral geometry).
The latter has a
unique independent silver(I) ion in a tetrahedral environment,
with two
coordinated PPh3 ligands. The reactivity of known silver(I)
azolates
with PPh3, as well as the solution behaviour and (when
available) the
crystal structures of the corresponding derivatives are
taken into
consideration for a due comparison.
2004-125
Gredin, P Labeguerie, J Pierrard, A
Vaulay, MJ de Kozak, A
Synthesis and structural characterization of K0.33Gd0.67F2.33 (KGd2F7)
and K0.31Gd0.69F1.84O0.27
SOLID STATE SCIENCES 6, 2004, 1221-1228.
K0.33Gd0.67F2.33(KGd2F7) is synthesized by solid state reaction between
KF and GdF3 at different temperatures (600, 700, 800 and
900 degreesC).
For all temperatures, the crystal structure of K0.33Gd0.67F2.33
derives
from that of the fluorite type. Nevertheless when the
synthesis
temperature increases, the X-ray powder pattern exhibits
new
superstructure diffraction lines. This feature is attributed
to an
anionic and cationic ordering. A structural model is elaborated
and the
crystal structure at 700 degreesC is determined by the
Rietveld method.
The oxyfluoride K0.31Gd0.69F1.83O0.27 is synthesized using
a sol-gel
route. Its crystal structure is close to that of K0.33Gd0.67F2.33
and
differs only by a new anionic and cationic ordering. K0.33Gd0.67F2.33
and K0.31Gd0.69F1.83O0.27 are then just particular compositions
of the
solid solution formulated K1-xGdxF1+2x-2yOy.
2004-126
Broach, RW Sinkler, W Patton, RL
Mezza, TM Gatter, MG
Technique integration applied to structure solution: The case of UZM-5.
Details of the structure, faulting and templating
RECENT ADVANCES IN THE SCIENCE AND TECHNOLOGY OF ZEOLITES AND RELATED
MATERIALS, PTS A - C 154, 2004, 1188-1196.
The structure solution of the new zeolite framework UZM-5 is reviewed.
It is shown how the structure solution emerges from integration
of a
number of zeolite characterization techniques such as
powder X-ray
diffraction, transmission electron microscopy, infrared
spectroscopy
and McBain adsorption. In addition to the ideal structure,
faulting is
evident in both powder X-ray diffraction and transmission
electron
microscopy. Details of the surface structure and faulting
on the (001)
planes are described.
2004-127
Hoyos, D Paillaud, JL Guth, JL
Synthesis and structure determination of a novel lithium copper
vanadate LiCu2VO4(OH)(2)
SOLID STATE SCIENCES 6, 2004, 1359-1364.
A novel lithium copper vanadate LiCu2VO4(OH)(2) (I) and Volborthite
Cu3V2O7(OH)(2) are two phases obtained at 170degreesC
by hydrothermal
synthesis during the study of the CuO; V2O5; U2O; H2O
system. Compound
(1) crystallizes in the orthorhombic system, with the
space group
P2(1)2(1)2(1) (No. 19) and with the unit-cell parameters
a = 9.6086(2)
Angstrom, b = 8.4482(2) Angstrom, c = 5.8938(1) Angstrom.
The structure
was determined from powder by an "ab initio" method using
the EXPO
software and refined with GSAS, a Rietveld refinement
package.
Wave-like layers of rutile-type copper chains sharing
vertex with the
neighbor chains, are linked into a three-dimensional framework
by rows
of alternating tetrahedra of vanadium and trigonal bipyramids
of
lithium which share edges and vertices with the copper
octahedra.
2004-128
Chernyshev, VV Stephens, PW Yatsenko, AV
Ryabova, OB Makarov, VA
Structural characterization of prazosin hydrochloride and prazosin
free
base
JOURNAL OF PHARMACEUTICAL SCIENCES 93, 2004, 3090-3095.
three-dimensional solid-state structures of prazosin hydrochloride,
C19H22N5O4+ . Cl- (A), and prazosin free base, C19H21N5O4
(B), have
been determined by synchrotron X-ray powder diffraction.
A and B
crystallize in triclinic P-1 and monoclinic Cc space groups,
respectively, with one structural unit per asymmetric
part. In A and B,
the prazosin molecule adopts different conformations,
which do not
correspond to those obtained by DFT optimizations of protonated
and
free prazosin.
2004-129
Nomiya, K Yoshizawa, A Tsukagoshi, K
Kasuga, NC Hirakawa, S Watanabe, J
Synthesis and structural characterization of silver(I), aluminium(III)
and cobalt(II) complexes with 4-isopropyltropolone (hinokitiol)
showing
noteworthy biological activities. Action of silver(I)-oxygen
bonding
complexes on the antimicrobial activities
JOURNAL OF INORGANIC BIOCHEMISTRY 98, 2004, 46-60.
Through two unequivalent oxygen donor atoms of the hinokitiol (Hhino;
C10H12O2; 4-isopropyltropolone) ligand that showed noteworthy
biological activities, the dimeric, silver(l)-oxygen bonding
complex
[Ag(hino)](2) 1, the monomeric aluminium(III) complex
[AI(hino)(3)] .
0.5H(2)O 4 and the cobalt(II) complex "[Co(hino)(2)](2)
. H2O" 6 were
synthesized and characterized with elemental analysis,
thermogravimetric and differential thermal analysis (TG/DTA),
FTIR and
solution (H-1 and C-13) NMR spectroscopy. The crystal
structure of 1
was determined by Rietveld analysis based on X-ray powder
diffraction
(XPD) data and those of [Al(hino)(3)] . MeOH 4a and
[Co(hino)(2)(EtOH)](2) 6a, being obtained as yellow block
crystals and
red platelet crystals, respectively, by crystallization
of 4 and 6,
were determined by single-crystal X-ray analysis. The
antimicrobial
activities of 1, 4 and 6, evaluated with minimum inhibitory
concentration (MIC; mug ml(-1)), were compared with those
of other
metal complexes (M = Na, Li, Cs, Ca, V, Zn) with the hino(-)
ligand.
The antimicrobial activities observed in the alkali-metal
salts
strongly suggested that they were attributed to the effect
of the
anionic hino- species. The antimicrobial activities of
1 were
significantly enhanced, whereas those of other metal complexes
were
suppressed, compared with those of the neutral Hhino and
anionic hino-
molecules. The antimicrobial activities observed in I
were comparable
with those of other recently found silver(l)-oxygen bonding
complexes,
the ligands of which had no activity. Thus, it is proposed
that the
antimicrobial activities of the silver(l)-oxygen bonding
complexes are
due to a direct interaction or complexation of the silver(l)
ion with
biological ligands such as protein, enzyme and membrane,
and the
coordinating ligands of the silver(l) complexes play the
role of a
carrier of the silver(l) ion to the biological system.
2004-130 ???
Clavier, N Dacheux, N Martinez, P
de Kerdaniel, EDF
Aranda, L Podor, R
Sintering of beta-thorium-uranium(IV) phosphate-diphosphate solid
solutions from low-temperature precursors
CHEMISTRY OF MATERIALS 16, 2004, 3357-3366.
Pure and single phase thorium-uranium(IV) phosphate-diphosphate
beta-TUPD (orthorhombic form) dense pellets were prepared
by two wet
chemical routes from low-temperature precursors. The first
method was
based on the "direct evaporation" of a mixture containing
tetravalent
actinides and phosphoric acid while the second one involved
the initial
precipitation of the thorium-uranium(IV) phosphate-hydrogenphosphate
hydrate (TUPHPH). Both methods led to single phase sintered
samples
following a two-step procedure using a uniaxial pressing
at room
temperature and then a heat treatment at high temperature.
The
dilatometric study and the determination of the linear
shrinkage of the
pellets showed that the best densification of the samples
prepared via
the "precipitation" method was obtained after heating
the raw pellet at
1250 degreesC for 5 h, for initial uranium amount lower
than 44.5 wt
%(U). For samples prepared via "direct evaporation", the
heat treatment
must be prolonged for at least 15 h at this temperature.
Moreover, the
complete characterization of the samples (EPMA, and so
forth) confirmed
that the homogeneity of the samples was significantly
improved when
using TUPHPH as a precursor, probably due to the better
reactivity of
the initial powder (higher specific surface area, smaller
grain size,
and so forth). Several leaching tests were performed in
various acidic
media and in natural waters on beta-TUPD sintered samples.
All the
corresponding normalized dissolution rates remained low
(10(-6) to
10(-5) g/(m(2) day)) even in aggressive media which confirms
the high
chemical durability of beta-TUPD, thus enhancing the potential
use of
this ceramic in the field of the efficient immobilization
of
tetravalent actinides.
2004-131
Bull, CL McMillan, PF Soignard, E
Leinenweber, K
Determination of the crystal structure of delta-MoN by neutron
diffraction
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 1488-1492.
We have determined the crystal structure of ordered hexagonal delta-MoN
by use of powder X-ray diffraction and time-of-flight
neutron
diffraction. A disordered variety of the compound was
first prepared by
high-temperature ammonolysis Of MoCl5. This material has
hexagonal
symmetry with the space group P6(3)mc with a = 2.87(2)
and c = 2.81 (1)
Angstrom. Upon high pressure annealing, the N-atoms become
ordered and
the unit cell doubles in size: a = 5.73659(10) and c =
5.61884(17)
Angstrom. The superconducting transition temperature increases
from 4K
in the disordered compound to 12.1 K in the ordered phase.
2004-132
Ling, CD Johnson, M
Modelling, refinement and analysis of the "Type III"
delta-Bi2O3-related superstructure in the Bi2O3-Nb2O5
system
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 1838-1846.
The structure of the "Type III" delta-Bi2O3-related superstructure
phase in the system Bi2O3-Nb2O5 is presented. A starting
model was
constructed by considering the crystal-chemistry of the
system in the
context of symmetry constraints determined by electron
diffraction.
After applying initial distortions, this could be Rietveld-refined
against a combination of synchrotron X-ray and time-of-flight
neutron
powder diffraction data. The undistorted starting model
was
independently optimized using solid-state ab initio energy
calculations, giving a fully optimized structure in excellent
agreement
with that obtained by Rietveld refinement. This dual approach
both
validates the structure and demonstrates the value of
combining
accurate total energy calculations with traditional refinement
techniques for the solution of complex structures using
powder
diffraction data. The structure (Bi94Nb32O221, Z = l,
I (4) over bar m2
(#119), a = 11.52156(18), c = 38.5603(6) A) consists of
interacting
corner-connected strings of NbO6 octahedra along <110>(F)
directions of
the FCC subcell, and can be described as a hybrid of fluorite
and
pyrochlore types.
2004-133
Hong, SB Lear, EG Wright, PA Zhou,
WZ Cox, PA
Shin, CH Park, JH Nam, IS
Synthesis, structure solution, characterization, and catalytic
properties of TNU-10: A high-silica zeolite with the STI
topology
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126, 2004, 5817-5826.
A high-silica zeolite (Si/Al = 7.1) with the STI framework topology,
denoted TNU-10, has been synthesized in the presence of
1,4-bis(N-methylpyrrolidinium)butane and Na+ cations as
structure-directing agents, and its structure in the proton
form has
been refined against laboratory powder X-ray data in space
group Fmmm
(a = 13.533(1) Angstrom, b = 17.925(2) Angstrom, c = 17.651(2)
Angstrom). The space group symmetry is supported by electron
diffraction and energy minimization studies. The as-made
and proton
form of TNU-10 are extensively characterized by elemental
and thermal
analyses, scanning electron microscopy, N-2 adsorption,
multinuclear
solid-state NMR, IR, and temperature-programmed desorption
of ammonia,
and the location of the organic structure-directing agent
in the
channel system is determined by molecular modeling. The
catalytic
properties of H-TNU-10 and Co-TNU-10 are evaluated for
the skeletal
isomerization of 1-butene to isobutene and the selective
reduction of
NO with methane, respectively. When compared to H-ferrierite,
a low
selectivity to isobutene is observed for H-TNU-10. However,
it is found
that Co-TNU-10 exhibits a maximum NO conversion of 93%
at 823 K under
conditions of high concentrations of methane (16000 ppm)
and water
vapor (10%) and in the presence of 2.6% O-2, which is
considerable
higher than even the value (74%) obtained from Co-ferrierite,
known as
the best catalyst for this reaction, under the identical
conditions.
2004-134
Mogare, KM Friese, K Klein, W Jansen,
M
Syntheses and crystal structures of two sodium ruthenates: Na2RuO4
and
Na2RuO3
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 630, 2004, 547-552.
Na2RuO4, prepared from Na2O2 and RuO2 via high oxygen pressure
synthesis, crystallises monoclinic in space group P2(1)/c
(a =
10.721(6), b = 7.033(4), c = 10.871(6) Angstrom, beta
=
119.10(4)degrees, Z = 8, 2503 unique reflections, R-1
= 0.049).
Structure determination from single crystal data shows
that the
compound consists of infinite chains of RuO5 trigonal
bipyramids
connected through their axial vertices. The Na cations
connect the
pseudohexagonally packed (1)(infinity)[RuO3O2/2] chains
and are
coordinated by six or seven oxygen atoms, respectively.
The compound
exhibits an one-dimensional spin system with mu = 2.80
mu(B) and Theta
= -222 K and a three-dimensional antiferromagnetic ordering
below 50 K.
Na2RuO3 was obtained from Na2RuO4 at 850 degreesC under
a flow of
argon. The structure was determined from X-ray powder
diffraction. It
is closely related to the alpha-NaFeO2 and the Li2SnO3
structure types,
layered variants of the NaCl type. In Na2RuO3 the Na and
Ru atoms are
partially disordered. This partially disordered state
was approximated
by a Rietveld refinement of two superimposed structural
models (model
I: R (3) over bar m, a = 3.12360(5), c = 16.0370(4) Angstrom,
Z = 2;
model II: C2/c, a = 5.4141(4), b = 9.3663(6), c = 10.8481(4)
Angstrom,
beta = 99.636(9)degrees, Z = 8).
2004-135 ???
Zima, V Melanova, M Benes, L Trchova,
M Dybal, J
Intercalation of gamma-butyrolactone into vanadyl phosphate and niobyl
arsenate
EUROPEAN JOURNAL OF INORGANIC CHEMISTRY iss 3, 2004, 570-574.
Intercalation compounds of vanadyl phosphate and isostructural niobyl
arsenate with gamma-butyrolactone, VOPO4.C4H6O2 and NbOAsO4.C4H6O2,
respectively, were prepared from corresponding propanol
intercalates by
molecular exchange in a microwave field. The prepared
intercalates were
characterized using powder X-ray diffraction, density
measurements, and
thermogravimetric analysis. Infrared and Raman spectra
indicate a
coordination of the carbonyl oxygen atom of the gamma-butyrolactone
molecule to the vanadium or niobium atom of the host structure.
Quantum
mechanical calculations at the ab initio level confirm
the proposed
structure in which the I-butyrolactone guest molecules
are arranged
with the plane of the ring perpendicular to the host layers
and are
anchored to the layers through the carbonyl oxygen atom
coordinated to
the transition metal atom of the host.
2004-136
Dova, E Peschar, R Sakata, M Kato,
K Stassen, AF
Schenk, H Haasnoot, JG
Structures of Fe-II spin-crossover complexes from synchrotron
powder-diffraction data
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 60, 2004, 528-538.
Crystal structure determination and analysis have been carried out
for
the two spin-crossover compounds [Fe(teeX)(6)](BF4)(2)
(teeX is
haloethyltetrazole; X = I: teei; X = Br: teeb), in both
their high-spin
(near 300 K) and their low-spin states (T = 90 K), using
high-resolution powder-diffraction data collected at the
ESRF
(Grenoble, France) and SPring8 (Japan) synchrotron radiation
facilities. The structures of teei have been solved using
various
direct-space structure determination techniques (grid
search genetic,
algorithm and parallel tempering) and refined with the
Rietveld method
using geometrical restraints. In the case of teeb, a structural
model
was found but a full refinement was not successful because
of the
presence of a significant amount of an amorphous component.
Analysis of
the structures (space group P2(1)/c, Z = 2) and diffraction
data, and
the absence of phase transitions, show the overall structural
similarity of these compounds and lead to the conclusion
that the
gradual spin-crossovers are likely to be accompanied by
small
structural changes only.
2004-137
Xu, HW Nyman, M Nenoff, TM Navrotsky,
A
Prototype sandia octahedral molecular sieve (SOMS) Na2Nb2O6-H2O:
Synthesis, structure and thermodynamic stability
CHEMISTRY OF MATERIALS 16, 2004, 2034-2040.
A new microporous phase Na2Nb2O6.H2O, which transforms to NaNbO3
perovskite on heating, has been synthesized by the hydrothermal
method.
Rietveld analysis of powder synchrotron X-ray diffraction
data reveals
that the structure comprises a framework of [NbO6] and
[NaO6] pctahedra
with other Na+ being located in the channels (space group
C2/c; a =
17.0511(9) Angstrom; b = 5.0293(2) Angstrom; c = 16.4921(9)
Angstrom;
beta =113.942(2)degrees). This phase belongs to the recently
synthesized Sandia octahedral molecular sieves (SOMS)
family,
Na2Nb2-xMxO6-x(OH)(x).H2O (M = Ti, Zr) and is the archetype
for the
substituted structures. Using drop-solution calorimetry
into molten
3Na(2)O.4MoO(3) at 974 K, the enthalpies of formation
of Na2Nb2O6.H2O
from the constituent oxides and from the elements have
been determined
to be -295.4 +/- 4.8 and -2895.5 +/- 6.4 kJ/mol, respectively.
From the
drop-solution calorimetric data for Na2Nb2O6.H2O and its
dehydrated
perovskite phase, the enthalpy of the dehydration reaction,
Na2Nb2O6.H2O --> 2NaNbO(3) + H2O, has been derived, and
its
implications for phase stability are discussed.
2004-138
Christensen, M Iversen, BB Bertini, L
Gatti, C Toprak, M
Muhammed, M Nishibori, E
Structural study of Fe doped and Ni substituted thermoelectric
skutterudites by combined synchrotron and neutron powder
diffraction
and ab initio theory
JOURNAL OF APPLIED PHYSICS 96, 2004, 3148-3157.
We present neutron and synchrotron powder-diffraction investigations
as
well as ab initio calculations to elucidate delicate structural
features in doped skutterudites. Samples with assumed
Fe doping were
investigated (FeyCo4Sb12, y=0.4, 0.8, 1.0, and 1.6), as
well as samples
with formal Ni substitution (Co4-xNixSb12, x=0, 0.4, 0.8,
and 1.2). The
present study serves as a case story for the determination
of fine
structural details of thermoelectric skutterudites by
diffraction
methods in combination with ab initio calculations. We
illustrate the
problem of fluorescence in the conventional x-ray powder
diffraction on
the Fe-doped samples by a comparison with the neutron
powder-diffraction data. On the series of the Ni-substituted
samples,
the neutron powder-diffraction data were collected to
investigate the
exact sitting of the Ni. The sample with the highest Ni
substitution
(Co2.8Ni1.2Sb12) was also used for high resolution, high-energy
synchrotron powder diffraction measurements. These revealed
that the
sample consists of two skutterudite phases. A complete
description of
the Ni-substituted samples was obtained in tandem with
ab initio
calculations, which show that the system contains a Ni-rich
(Co0.38Ni3.62Sb12) and a Ni-poor (Co3.76Ni0.24Sb12)) skutterudite
phases.
2004-139
Cernak, J Gerard, F Kappenstein, C
Chomic, J
Copper/Zinc oxide catalysts. Part XII. Solid solution formation in
the
CuO/ZnO system. X-ray powder diffraction study
MONATSHEFTE FUR CHEMIE 135, 2004; 1081-1088.
Coordination compounds Zn(ma1)(H2O)(2) (ZMH) (mal=maleate anion
(C2H2(CO2)(2)(2-))), Cu0.06Zn0.94(mal)(H2O)(2) (ZCMH),
Cu(mal)(H2O)
(CMH), and physical mixtures of CMH and ZMH were used
as precursors for
calcination experiments in air at 500 and 1000degreesC
lasting 18
hours. The obtained oxides were investigated by X-ray
powder
diffraction technique. Calcination at 500degreesC yielded
pure zincite
phase (ZnO), tenorite phase (CuO), or their mixtures.
The calcination
of the Zn-rich sample ZCMH at 1000degreesC lead to zincite
phase
displaying a slightly lower cell volume than the pure
zincite phase
obtained from Zn-only containing precursor (ZMH). These
results suggest
that the assumed solid solution CuxZn1-xO (x=0.01-0.02)
exhibits a
solubility limit lower than the copper content in the
ZCMH precursor (6
mol-%). On the other hand, the calcination of the Cu-rich
samples at
1000degreesC, in the presence of Zn(II), yielded tenorite
phase
exhibiting cell parameters significantly different from
those reported
for the pure tenorite phase, due to the formation of Zn0.03Cu0.97O
solid solutions. All these results are corroborated by
intensity
analysis of the diffraction peaks.
2004-140
Pfeffer-Hennig, S Piechon, P Bellus, M
Goldbronn, C Tedesco, E
Physico-chemical characterization of an active pharmaceutical
ingredient - Crystal polymorphism and structural analysis
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY 77, 2004, 663-679.
The physico-chemical properties and polymorphism of a new active
pharmaceutical ingredient entity has been analyzed and
the gain of
knowledge during the chemical development of the substance
is
described. Initial crystallization revealed an anhydrous
crystal form
with good crystallinity and a single, sharp DSC melting
peak at 171
degreesC and a straightforward development of this crystal
form seemed
possible. However, during polymorphism screening, new
crystalline forms
were detected that were often analyzed as mixtures of
crystal forms.
The process of characterization and identification of
the different
crystalline forms and its thermodynamical relationship
has been
supported by a combination of experimental and computational
work
including determination of the three-dimensional structures
of the
crystal forms. The crystal structure of one polymorphic
form was solved
by single crystal X-ray structure analysis. Unfortunately,
Mod B
resisted in formation of suitable single crystals, but
its structure
could be solved by high resolution powder diffraction
data analysis
using synchrotron radiation. Calculation of the theoretical
X-ray
powder diffraction pattern from three dimensional crystal
coordinates
allowed an unambiguous identification of the different
crystalline
forms. Two polymorphic crystal forms of the API-CG3, named
Mod A and
Mod B, are enantiotropic whereas Mod B is the most stable
polymorph at
room temperature up to about 50 degreesC and Mod A at
temperatures
above 50 degreesC. The mechanism of the solid - solid
transition can be
explained by analyzing the molecular packing information
gained from
the single crystal structures. A third crystalline form
with the
highest melting peak turned out to be not a polymorphic
or
pseudopolymorphic crystal modification of our API-CG3
but a chemically
different substance.
2004-141
Schobinger-Papamantellos, P Rodriguez-Carvajal, J
Andre, G
Ritter, C Buschow, KHJ
Re-entrant magneto-elastic transition in HoFe4Ge2 a neutron diffraction
study
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 280, 2004, 119-142.
The re-entrant magneto-elastic transition of the antiferromagnetic
HoFe4Ge2 compound has been studied by neutron powder diffraction
as a
function of temperature. The magnetic phase diagram comprises
the wave
vectors: (q(1o), q(2o), q(1t)) and three magnetic transitions,
two of
them occurring simultaneously with the structural changes
at T-c, T-N =
52 and T-c', T-ic1 = 15 K, the third being purely magnetic
at T-ic2 =
40 K. The first transition is of second order while the
latter two of
first order. The sequence of phases follows the path:
P4(2)/mnm (HT),
T-c, T-N = 52 K --> Cmmm (IT): (q(1o) = (0, 1/2, 0) T-ic2
= 40 K double
right arrow q(2o) = (0, q(y), 0)), T-c', T-ic1 = 15 K
double right
arrow P4(2)/mnm (LT): q(1t) = (0, 1/2, 0). The magnetic
structures
described by the wave vectors (q(1o), q(2o) and q(1t)),
where the
components are referred to the reciprocal basis of the
conventional
Cmmm cell, correspond to canted multi-axial arrangements.
The q(2o)
wave vector length of the amplitude modulated phase varies
non-monotonously, decreasing fast just below T-ic2,-slowly
between
36K-T-c', T-ic1 and jumping to the q(1t) = (0, 1/2,0)
lock-in value at
T-c', T-ic1 simultaneously with the first order re-entrant
transition
to the (LT) tetragonal phase. In the coexisting meta-stable
orthorhombic phase from T-c', T-ic1 down to 1.5 K the
length of the
wave vector q(2o) continues to decrease. To solve the
magnetic
structures of all the phases appearing in this complex
situation,
arising from competing ordering mechanisms and anisotropies
of the
underlying sublattices, we have used the simulated annealing
method of
global optimisation on high-resolution neutron powder
diffraction data.
2004-142
Pirozzi, B Napolitano, R Petraccone, V
Esposito, S
Determination of the crystal structure of syndiotactic
3,4-poly(2-methyl-1,3-butadiene) by molecular mechanics
and X-ray
diffraction
MACROMOLECULAR CHEMISTRY AND PHYSICS 205, 2004, 1343-1350.
The crystal structure of syndiotactic 3,4-poly(2-methyl-1,3-butadiene)
has been determined by the joint use of molecular mechanics
and X-ray
diffraction. Molecular mechanics calculations have been
performed both
on the isolated chain and on the crystal by the use of
various force
fields. The energy minimizations predict a model of the
crystal
structure. The calculated X-ray powder diffraction pattern
is in good
agreement with the experiment one. This model had been
refined in order
to obtain the best agreement with all the experimental
data. The space
group id Pbcm and the parameters of the unit cell are
a = 6.6 Angstrom,
b = 13.2 Angstrom, c = 5.27 Angstrom. The presence of
defects in the
crystal has been taken into account. Analogies and differences
with the
crystal structure of syndiotactic 1,2-poly(1,3-butadiene)
are discussed.
2004-143
Weirich, TE
The crystal structure of Zr2Se reinvestigated by electron
crystallography and X-ray powder diffraction
CRYSTALLOGRAPHY REPORTS 49, 2004, 379-389.
The metal-rich compound Zr2Se is of particular interest for electron
crystallography, since it was one of the first examples
that proved
that heavy-atom structures can be solved via quasi-automatic
direct
methods from selected area electron diffraction intensities
[1]. For
this reason, Zr2Se has been chosen as a model to discuss
the
possibilities and the limits of the quasi-kinematical
approach that has
been successfully used to determine this and related structures
from
high-resolution electron microscopy (HREM) images and
selected area
electron diffraction. In order to quantify the achievable
accuracy of
the electron crystallography techniques used, the corresponding
structures are compared with results from structural analysis
with
X-ray powder data and with a model received from first-principles
calculations. The latter structure was chosen in this
study as a
reference, since the calculations do not depend on experimental
parameters. Analysis of the obtained result from electron
diffraction
structural analysis (EDSA) shows that the structural model
is, on
average, only off by 0.08 Angstrom, despite the investigated
crystal
having an effective thickness of 286 Angstrom. The corresponding
result
from Rietveld refinement with X-ray powder data agrees
to within 0.04
Angstrom with the structure from calculation and within
0.03 Angstrom
with the result from an earlier single crystal X-ray study
[2].
2004-144
Rius, J Elkaim, E Torrelles, X
Structure determination of the blue mineral pigment aerinite from
synchrotron powder diffraction data: The solution of an
old riddle
EUROPEAN JOURNAL OF MINERALOGY 16, 2004, 127-134.
The structure of aerinite, a blue fibrous silicate mineral associated
with the alteration of ophitic rocks in the southern Pyrenees,
has been
determined by applying the direct methods modulus sum
function to
synchrotron powder diffraction data. This mineral was
the blue pigment
commonly used in most Catalan romanic paintings between
the XI-XV
centuries. The studied specimen comes from the Camporrells-Estopanya
area (Huesca, Spain). The unit cell dimensions are a =
b = 16.8820(9),
c = 5.2251(3) Angstrom, the space group is P3c1 and the
structural
formula is (Ca5.1Na0.5)(Fe3+AlFe2+ Mg-1.7(0.3))(Al5.1Mg0.7)
[Si12O36(OH)(12)H].[(CO3)(1.2)(H2O)(12)] With Z = 1 and
D-c = 2.52
g/cm(3) (Fe2+/Fe3+ ratio from Mossbauer spectroscopy;
carbonate content
confirmed by infrared spectroscopy). The model of the
structure
obtained by direct methods was refined with the Rietveld
method to the
residual value R-wp = 0.0937 (chi(2) = 1.05). A bond valence
analysis
shows the plausibility of the refined model.
The crystal structure of aerinite can be best understood
by introducing
cylindrical basic building units consisting on three pyroxene
chains
pointing inwards to accommodate tri- and divalent metal
cations at the
centres of the resulting face-sharing octahedra. The average
composition of these cationic sites is Fe3+ (0.25),Al3+
(0.25),Fe2+
(0.43),Mg2+ (0.07), the mean cation-oxygen bond length
is 2.054(9)
Angstrom and the intercationic distance is 2.61 Angstrom.
Out of the
three symmetry-independent three-fold rotation axes in
the unit cell,
two are occupied by such cylindrical units and the third
by CO3 groups.
Consequently, each unit is surrounded by three similar
ones which are,
however, shifted by 0.93 Angstrom along c. Between two
such units,
i.e., tangential to both cylindrical envelopes, a four-row
wide slab of
a brucite-like layer is found. The two inner octahedra
are
predominantly filled with Al and Mg atoms, the two outer
with Ca, Na
and some vacancies [average values: d(Al-O) = 1.936(53)
Angstrom (6x),
angle(O-Al-O) = 90.1(6.5)degrees (12x) and 172.7(4.1)degrees
(3x);
d(Ca-O) = 2.42(6) Angstrom (6x), angle(O-Ca-O) = 90(23)degrees
(12x)
and 158(14)degrees (3x)]. The internal O atoms of the
brucite-like
layer are hydroxyl groups, the intermediate are unshared
basal O atoms
of the neighbouring pyroxene chains, while the external
ones are water
molecules forming relatively strong H-bridges with the
partially
disordered CO3 groups. Presumably, the hydroxyl groups
in the
brucite-like layer also form H-bridges with the apical
O atoms of the
neighbouring pyroxene chains to compensate for the defect
of charge
caused by the presence of divalent cations in the face-sharing
octahedra.
2004-145
Sainz-Diaz, CI Villacampa, A Otalora, F
Crystallographic properties of the calcium phosphate mineral, brushite,
by means of First Principles calculations
AMERICAN MINERALOGIST 89, 2004, 307-313?
A crystalline form of hydrated calcium phosphate, brushite
(CaHPO(4)(.)2H(2)O), has been studied by means of total
energy First
Principles calculations based on the Density Functional
Theory (DFT)
approximation. The experimental crystal lattice parameters
of this
mineral have been reproduced with good agreement. The
powder X-ray
diffraction pattern simulated from the calculated crystal
structure is
similar to the experimental one. The intermolecular interactions
within
the crystal, electrostatic and hydrogen bond interactions,
have been
reproduced. The calculated crystal structure reproduces
the atomic
distribution along the (010) surface observed by high
resolution
scanning force microscope (SFM). The optimized crystal
structure
describes the different interatomic interactions along
the [101],
[201], and [001] directions on the (010) plane. Quantum-mechanical
calculations of the energy of these surfaces confirm the
experimental
behavior, justifying the different crystal growth rates
of these
directions found experimentally.
2004-146
Du, HL Han, JZ Zhang, WY Wang, CS
Wang, WC Liu, SQ
Chen, HY Zhang, XD Yang, YC
Determination of the zirconium site in zirconium-substituted
Nd(Fe,Mo,Zr)(12) compounds
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS 283, 2004, 316-321.
The NdFe10.5Mo1.5-xZrx (x = 0.25,0.50) and Nd0.5Pr0.5Fe10.5-xMo1.5Zrx
(x = 0, 0.25, 0.75, and 1.00) intermetallic compounds
with ThMn12-type
structures were successfully synthesized. Their structures
were
investigated by using powder X-ray diffraction. It is
found that Zr is
incorporated as a substituent for Nd/Pr in the structure
of the two
series, and the occupation of Zr is influenced by the
prepared
composition of Fe and the third element Mo. The effects
of Zr on the
magnetic properties were also studied.
2004-147
Breza, M Biskupic, S
On the structure of tetralead(II) complexes with OH bridges
COLLECTION OF CZECHOSLOVAK CHEMICAL COMMUNICATIONS 69, 2004, 2045-2054.
Using Hartree-Fock, B3LYP and MP2 treatments, the optimal geometries
and corresponding electronic structures of tetrahedral
[Pb-4(mu(3)-OH)(n)](q) and [Pb4O(mu(3)-OH)(n)](q-2) complex
cations
with total charges q = 8 - n, n = 2, 3, 4, are investigated.
After OH-
removal, the central oxygen atom in [Pb4O(mu(3)-OH)(4)](2+)
is shifted
to the apical position in [Pb4O(mu(3)- OH)(3)](3+) whereas
the
[Pb-4(mu(3)-OH)(2)](6+) and [Pb4O(mu(3)-OH)(2)](4+) complex
cations are
unstable. Direct Pb-Pb and O-O interactions are weakly
antibonding in
all the systems under study. The clusters are held together
exclusively
by relatively weak Pb-O bonds. A higher stability of the
complex
cations with a larger number of OH- bridges may be confirmed.
2004-148
Breza, M Biskupic, S
On the structure of boat-shaped hexalead(II) cations with OH bridges
COLLECTION OF CZECHOSLOVAK CHEMICAL COMMUNICATIONS 69, 2004, 2055-2067.
Using Hartree - Fock, B3LYP, and MP2 treatments, the optimal
boat-shaped geometries and corresponding electronic structures
of
[Pb6Om(mu(3)-OH)(n)](q) complex cations with total charges
q = 12 - 2m
- n, m = 0 or 1, n = 6 or 8, are investigated. Whereas
the
[Pb-6(mu(3)-OH)(6)](6+) cation is unstable, the remaining
structures
preserve C-2v symmetry. Direct Pb - Pb interactions are
weakly
antibonding in all the systems under study. The clusters
are held
together exclusively by relatively weak Pb - O bonds.
The effects of
central O and two additional mu(3)-OH bridges in
[Pb6O(mu(3)-OH)(8)](2+) are not fully cooperative.
[Pb6O(mu(3)-OH)(6)](4+) and [Pb-6(mu(3)-OH)(8)](4+) may
coexist in
water solutions in comparable concentrations.
2004-149
Laco, JII
Crystal structures of poly(n-methylen-di-O-methyl-L-tartaramide)s with
n=3, 5, 7 and 9
POLYMER 45, 2004, 7025-7033
The structural characterization of
poly(n-methylen-di-O-methyl-L-tartaramide)s with n = 3,
5, 7 and 9 has
been carried out using optical microscopy, thermal analysis,
X-ray
diffraction and electron microscopy. X-ray diffraction
of powder and
fiber samples were analyzed together with electron diffraction
patterns
of single crystals obtained from isothermal crystallization
in
solution. Experimental results based on crystallographic
data were used
to build a crystal model using the Cerius program. This
model is based
in chain packing with an arrangement of hydrogen-bonded
sheets, being
the resultant crystal structure similar to the exhibited
in
conventional polyamides.
2004-150
Abakumov, AM Rozova, MG Chizhov, PS
Antipov, EV Hadermann, J Van Tendeloo, G
Synthesis and crystal structure of the novel Pb5Sb2MnO11 compound
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 2855-2861.
The new Pb5Sb2MnO11 compound was synthesized using a solid-state
reaction in an evacuated sealed silica tube at 650degreesC.
The crystal
structure was determined ab initio using a combination
of X-ray powder
diffraction, electron diffraction and high-resolution
electron
microscopy (a = 9.0660(8) Angstrom, b = 11.489(1) Angstrom,
c =
10.9426(9) Angstrom, S.G. Cmcm, R-1 = 0.045, R-P = 0.059).
The
Pb5Sb2MnO11 crystal structure represents a new structure
type and it
can be considered as quasi-one-dimensional, built up of
chains running
along the c-axis and consisting of alternating Mn+2O7
capped trigonal
prisms and Sb2O10 pairs of edge sharing Sb+5O6 octahedra.
The chains
are joined together by Pb atoms located between the chains.
The Pb+2
cations have virtually identical coordination environments
with a clear
influence of the lone electron pair occupying one vertex
of the PbO5E
octahedra. Electronic structure calculations and electron
localization
function distribution analysis were performed to define
the nature of
the structural peculiarities. Pb5Sb2MnO11 exhibits paramagnetic
behavior down to T = 5K with Weiss constant being nearly
equal to zero
that implies lack of cooperative magnetic interactions.
2004-151
Brize, V Georges, S Kodjikian, S
Suard, E Goutenoire, F
La6Mo8O33: a new ordered defect Scheelite superstructure
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 2617-2627.
The structure of La6Mo8O33 has been determined from a triple pattern
powder diffraction analysis. Two high-resolution neutron
diffraction
patterns collected at 1.594 and 2.398 Angstrom and one
X-rays were
used. This molybdate crystallizes in a non-centrosymmetric
monoclinic
space group P2(1) (Ndegrees4), Z = 2, a = 10.7411(3) Angstrom,
b =
11.9678(3) Angstrom, c = 11.7722(3) Angstrom, beta = 116.062
(1)degrees. La6Mo8O33 is an unusual ordered defect Scheelite.
Hence, it
should be described with cation vacancies and an extra
oxygen atom
following the formula: La(6)rectangle(2)Mo(8)O(32+1).
This extra oxygen
atom leads to a pyramidal environment, whereas the other
molybdenum
atoms present tetrahedral environment. A molybdenum tetrahedral
is
connecting to the pyramid, forming an [Mo2O9] unit.
2004-152
Kamegashira, N Satoh, H Meng, J
Mikami, T
Structural determination of a new phase of monoclinic BaTb2Mn2O7
JOURNAL OF ALLOYS AND COMPOUNDS 374, 2004, 173-176.
A new phase of monoclinic BaTb2Mn2O7 with extra superlattice lines
in
addition to the usual orthorhombic X-ray diffraction patterns
was
prepared and a Rietveld refinement was applied to analyze
the crystal
structure using X-ray powder diffraction data at room
temperature. The
refined lattice parameters were a = 0.54918(8) nm, b =
2.0149(5) nm, c
= 0.54922(9) nm, and beta = 90.62degrees with the space
group A2/m (no.
12). The MnO6 oxygen octahedron has distortion and tilts
around a-axis
by about 7degrees each other in the reverse direction.
2004-153
Perchiazzi, N Gualtieri, AF Merlino, S
Kampf, AR
The atomic structure of bakerite and its relationship to datolite
AMERICAN MINERALOGIST 89, 2004, 767-776.
Four samples of bakerite, Ca4B5Si3O15(OH)(5), were studied by means
of
IR, TG/DSC, EPMA, and X-ray and neutron diffraction. Chemical
analyses
can readily discriminate bakerite from datolite, Ca4B4Si4O16(OH)(4),
by
the distinctly lower SiO2 content of the former. The Rietveld
refinement of the combined neutron and X-ray powder data
allow the
determination of the crystal structure of bakerite to
R-p 3.09%. The
crystal structure can be derived from that of datolite
by the
substitution 0.25Si(4+) + 0.25O(2-) <----> 0.25B(3+)
+ 0.25(OH)(-) at
the Si-centered tetrahedral site. This leads to the crystal
chemical
formula Ca(4)B(5)Si(3)0O(15)(OH)(5). Both of the two hydrogen
positions
in the bakerite structure, one with full occupancy, the
other with 25%
occupancy, were precisely located. The water molecule
generally thought
to be present in bakerite structure is actually absent.
The excess
water detected in chemical analyses can be attributed
to the presence
of minor impurities. Given the consistent composition
of bakerite from
various localities and no evidence for Substitution of
B for Si in
datolite, bakerite is retained as a distinct species.
A possible
explanation of the peculiar 5:3 boron to silicon ratio
in bakerite is
provided.
2004-154
Patoux, S Rousse, G Leriche, JB
Masquelier, C
Crystal structure and lithium insertion properties of orthorhombic
Li2TiFe(PO4)(3) and Li2TiCr(PO4)(3)
SOLID STATE SCIENCES 6, 2004, 1113-1120.
The crystal structures of orthorhombic Li2TiFe(PO4)(3) and
Li2TiCr(PO4)(3) were determined from Rietveld refinement
of neutron
powder diffraction data. Both compounds are isostructural
in the Pbna
space group with a = 8.543(1) Angstrom, b = 8.623(1) Angstrom,
c =
11.978(1) Angstrom and a = 8.505(1) Angstrom, b = 8.589(1)
Angstrom, c
= 11.929(1) Angstrom, respectively. Lithium ions are located
in a
single four-fold coordinated site Li(1). Electrochemical
insertion of
lithium proceeds through the reduction of Fe3+ into Fe2+
(similar to
2.8 V vs. Li+/Li) and Ti4+ into Ti3+ (similar to 2.5 V
vs. Li+/Li)
towards the new compositions Li3TiCr(PO4)(3) and Li4TiFe(PO4)(3).
In
situ X-ray diffraction and potentiostatic intermittent
titration
technique indicate a solid solution mechanism for the
reversible
lithium insertion/extraction. Chemical reaction of Li2TiFe(PO4)3
with
n-BuLi leads to orthorhombic Li4TiFe(PO4)3.
2004-155
Wallez, G Launay, S Quarton, M Dacheux,
N Soubeyroux, JL
Why does uranium oxide phosphate contract on heating?
JOURNAL OF SOLID STATE CHEMISTRY 177, 2004, 3575-3580.
(U2O)(PO4)(2) is related to ultra-low expansion beta-(Zr2O)(PO4)(2)
ceramics, but shows a continuous thermal contraction.
High-temperature
neutron diffraction has allowed to follow accurately the
thermal
variations of its cell edges and to give a structural
explanation to
the phenomenon: like in beta-(Zr2O)(PO4)(2), the dilatometric
anomaly
arises simultaneously from a contractive push-pull effect
due to
Coulombic repulsions and from a libration of the PO4 and
UO7 polyhedra,
but in the present case, the second mechanism predominates.
The size of
the tetravalent cation appears as a key parameter in monitoring
the
thermal expansion of ceramics of this family.
2004-156
Yan, W Lerner, MM
Synthesis and structural investigation of new graphite intercalation
compounds containing the perfluoroalkylsulfonate anions
C10F21SO3-,
C2F5OC2F4SO3-, and C2F5(C6F10)SO3-
CARBON 42, 2004, 2981-2987.
The preparation of graphite intercalation compounds (GIC's) of three
perfluorinated alkylsulfonate anions, C10F21SO3-, C2F5OC2F4SO3-
and
C2F5(C6F10)SO3- is described for the first time. Pure
stage 2 GIC's are
obtained by chemical oxidation of graphite with K2MnF6
in a solution
containing hydrofluoric and nitric acids for 72 h. One-dimensional
electron density maps derived from powder diffraction
data are fit to
obtain models for the intercalate gallery structures:
the structure
models provide details on anion concentrations, orientations,
and
conformations. In all cases, anion bilayers are observed
with anion
sulfonate headgroups oriented towards graphene sheets.
Compared with
structures calculated for the isolated anions, the intercalated
anion
conformations show changes in dihedral angles, involving
rotations
about C-C or C-O bonds. For the GIC containing C2F5(C6F10)SO3-,
the
anion conformation change is related to the more efficient
packing of
anions in the intercalate gallery.
2004-157
Tremayne, M
Direct space structure solution applications
JOURNAL OF RESEARCH OF THE NATIONAL INSTITUTE OF STANDARDS AND
TECHNOLOGY 109, 2004, 49-63.
The crystal structures of 2,4,6-triisopropyl-benzenesulfonamide,
1,2,3-trihydroxybenzenehexamethylenetetramine (1/1), 5-bromonicotinic
acid and chlorothalonil form II have been solved from
x-ray powder
diffraction data, by application of a direct space structure
solution
approach using the Monte Carlo method and confirmed by
Rietveld
refinement. In the sulfonamide, the molecules are linked
by N - H...O
hydrogen bonds into two-dimensional sheets built from
alternating eight
and twenty-membered rings. In the cocrystal, the molecules
are linked
by O-H...N hydrogen bonds to form puckered molecular ribbons
that are
in turn linked into a continuous 3D framework by C-H...pi
( arene)
interactions. 5-bromonicotinic acid also displays atypical
hydrogen-bonding behaviour by formation of dimers through
a
self-complementary acid-acid hydrogen-bond motif that
are connected
into antiparallel ribbons by C - H...O and C - H...N hydrogen
bonds.
Structure determination of the cocrystal and the bromonicotinic
acid
was successful despite the presence of preferred orientation
in the
data, whereas the distortion of the chlorothalonil data
was so severe
that structure solution was only possible when the effects
of preferred
orientation were minimized. Both the disordered structure,
and an
ordered structural approximation of chlorothalonil form
II have been
determined and rationalized.
2004-158 ???
Siwicka, A Reiter, RJ Tian, DX Wojtasiewicz,
K Leniewski, A
Maurin, JK Blachut, D Czarnocki,
Z
The synthesis and the structure elucidation of N,O-diacetyl derivative
of cyclic 3-hydroxymelatonin
CENTRAL EUROPEAN JOURNAL OF CHEMISTRY 2, 2004, 425-433.
Melatonin was subjected to an oxidation to give 3-hydroxymelatonin.
All
spectroscopic data for this compound were collected. Ab
initio
calculations for both possible configurations were performed.
X-ray
data on N, O-diacetyl derivative of 3-hydroxymelatonin
allowed the
unambigous structure determination.
2004-159
Muhle, C Karpov, A Nuss, J Jansen,
M
Crystal growth and crystal structure determination of
K-2[Pt(CN)(4)Cl-2], K-2[Pt(CN)(4)Br-2], K-2[Pt(CN)(4)I-2]
and
K-2[Pt(CN)(4)]Cl-2] . 2H(2)O
ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES
59, 2004, 567-572.
Crystals of K2Pt(CN)(4)Br-2, K2Pt(CN)(4)I-2 and
K2Pt(CN)(4)Cl(2)(.)2H(2)O were grown, and their crystal
structures have
been determined from single crystal data. The structure
of
K2Pt(CN)(4)Cl-2 has been determined and refined from X-ray
powder data.
All compounds crystallize monoclinicly (P2(1)/c; Z = 2),
and
K2Pt(CN)(4)X-2 with X = Cl, Br, I are isostructural. K2Pt(CN)(4)Cl-2:
a
= 708.48(2); b = 903.28(3); c = 853.13(3) pm; beta = 106.370(2)degrees;
R-p = 0.064 (N(hkl) = 423). K2Pt(CN)(4)Br-2: a = 716.0(1);
b =
899.1(1); c = 867.9(1) pm; beta = 106.85(1)degrees; R(F)(N')
= 0.026
(N'(hkl) = 3757). K2Pt(CN)(4)I-2: a = 724.8(1); b = 914.5(1);
c =
892.1(1) pm; beta = 107.56(1)degrees; R(F)(N') = 0.025
(N'(hkl) =
2197). K2Pt(CN)(4)Cl-2 (.) 2H(2)O: a = 763.76(4); b =
1143.05(6); c =
789.06(4) pm; beta = 105.18(1)degrees; R(F)(N') = 0.021
(N'(hkl) =
2281). Raman and infrared spectroscopy data are reported.
2004-160
Niewa, R Zherebtsov, DA
New phases in the lithiumnitridovanadate system - The solid solution
Li7-2xMgx[VN4] with 0 <= x <= 1
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 630, 2004, 229-233.
Solid solution phases Li7-2xMgx[VN4] (0 < x less than or equal to
1)
with varying Mg-content are obtained as yellow microcrystalline
powders
from heat treatment of mixtures of VN, Li3N and Mg3N2
or from mixtures
of Li-7[VN4] and Mg3N2 at 1370 K in N-2 atmosphere at
ambient pressure.
At substitution parameter values of x > 0.5 a subsequent
distortion
from the ideal cubic unit cell to an orthorhombic unit
cell is
observed. The crystal structure of Li7-2xMgx[VN4] with
x approximate to
1 was refined from neutron and X-ray powder diffraction
data (space
group Pbca, No. 61, a = 963.03(3) pm, b = 958.44(3) pm,
c = 951.93(2)
pm, neutron pattern 14degrees - 156degrees 2theta, step
non-linear
approximate to 0.0782degrees 2theta, No. of measured points
1816, R-p =
0.089, R-wp = 0.115, R-Bragg = 0.155, R-F = 0.114; X-ray
pattern
10degrees - 98degrees 2theta, step 0.005degrees 2theta,
No. of measured
points 17600, R-p = 0.028, R-wp = 0.045, R-Bragg = 0.113,
R-F = 0.133,
structure variables: 45). The crystal structure resembles
a Li2O type
superstructure with the atomic arrangement of beta-Li-7[VN4]
and with
two crystallographic Li-sites each substituted by Mg with
statistical
occupation factors of 0.5. Chemical analyses prove the
composition and
XAS spectroscopy at the V K-edge support the +5 oxidation
state
assignment for vanadium. XAS data also support the tetrahedral
coordination of vanadium by N as indicated by the structure
refinements.
2004-161
Le Berre, F Crosnier-Lopez, MP Fourquet, JL
Cationic ordering in the new layered perovskite BaSrTa2O7
SOLID STATE SCIENCES 6, 2004, 53-59.
BaSrTa2O7 is a new well-ordered layered perovskite synthesized by solid
state reaction. This phase derives from the Dion-Jacobson
family of
general formula A'[A(n-1)B(n)O(3n+1)] with B =Ta and n
=2 in which the
monovalent cation A' is replaced by one divalent cation.
The structure
was refined from X-ray powder diffraction data in the
orthorhombic
space group Immm (No. 71) with lattice constants a = 3.99372(5)
Angstrom, b = 7.8428(1) Angstrom and c = 20.1609(3) Angstrom
(Z = 4).
Although the similar Sr-O and Ba-O distances allow the
localization
inside or between the perovskite blocks for the two cations,
the X-ray
study reveals that the Ba2+ and Sr2+ ions are strictly
ordered: Ba2+
ions in an interlayer position (4j site) and Sr2+ ions
within the
perovskite blocks (2b and 2c sites). TEM study is undertaken
to verify
the local Ba2+/Sr2+ distribution (local ordering or population
fluctuations) and to check the possible existence of other
n members.
2004-162
Ferey, G Serre, C Mellot-Draznieks, C
Millange, F
Surble, S Dutour, J Margiolaki,
I
A hybrid solid with giant pores prepared by a combination of targeted
chemistry, simulation, and powder diffraction
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 43, 2004, 6296-6301.
2004-163
Brodski, V Peschar, R Schenk, H
Brinkmann, A van Eck, ERH
Kentgens, APM Coussens, B Braam,
A
Structure of melaminium dihydrogenpyrophosphate and its formation from
melaminium dihydrogenphosphate studied with powder diffraction
data,
solid-state NMR, and theoretical calculations
JOURNAL OF PHYSICAL CHEMISTRY B 108, 2004, 15069-15076.
Melaminium dihydrogenpyrophosphate (bis(2,4,6-triamino-1,3,5-triazinium
dihydrogenpyrophosphate, MPy), obtained as a crystalline
powder by
thermal treatment of melaminium dihydrogenphosphate (MP),
is the first
intermediate in the synthesis of polymerized melamine
phosphates that
are used as environmental-friendly flame retardants. The
crystal
structure of MPy was determined by X-ray powder diffraction
and the
proposed hydrogen-bonding model was corroborated by solid-state
NMR and
periodic DFT calculations. A mechanism is proposed for
the endothermic
dehydration process that takes place in the reaction from
MP to MPy, in
accordance with energy calculations based on the optimized
crystal
structures of MPy and MP. A packing analysis of MPy and
other
melamine-containing compounds revealed some typical melamine
packing
motifs.
2004-164
Schenk, H Peschar, R
Understanding the structure of chocolate
RADIATION PHYSICS AND CHEMISTRY 71, 2004, 829-835.
Crystallization of cocoa-butter in the beta phase from the melt under
static conditions is only possible using the memory effect
of
cocoa-butter. Under all other conditions polymorphs with
lower melting
temperatures develop, whereas the beta phase is the preferred
one in
chocolate. SAXS experiments proved 1,3-distearoyl-2-oleoylglycerol
seeds with triple chain-length packing initiate the
beta-crystallization. Models for the different phases
may be based on
the crystal structure determinations of triacylglycerols.
A new, patented, way of chocolate making is in development
in which the
traditional tempering process is replaced by another
pre-crystallization process. The process is based on the
use of seed
crystals in the liquid phase and driven by a feedback
system.
2004-165
De Ridder, DJA Goubitz, K Brodski, V
Peschar, R Schenk, H
Crystal structure of melaminium orthophosphate from high-resolution
synchrotron powder-diffraction data
HELVETICA CHIMICA ACTA 87, 2004, 1894-1905.
The crystal structure of melaminium orthophosphate (MP) has been
determined from high-resolution synchrotron powder-diffraction
data.
The crystal packing consists of melaminium layers and
pairs of
orthophosphate chains connected by H-bonds almost perpendicular
to the
layers. The distance between melaminium layers is 3.62
Angstrom.
Neighboring melaminium molecules do not lie in the same
plane, but in
two parallel planes at close distance (0.79 Angstrom),
and are shifted
with respect to each other. The orthophosphate chains
are connected by
both intra-chain and inter-chain H-bonds. The melamine
is singly
protonated at an endocyclic N-atom. The powder-diffraction
data were
corroborated by solid-state NMR experiments.
2004-166
Vos, TE Liao, Y Shum, WW Her, JH
Stephens, PW Reiff, WM Miller, JS
Diruthenium tetraacetate monocation, [Ru-II/(III)(2)(O2CMe)(4)](+),
building blocks for 3-D molecule-based magnets
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126, 2004, 11630-11639.
Diruthenium tetracarboxylates monocations are utilized as building
blocks for cubic 3-D network structured molecule-based
magnets.
[Ru-2(II/III)(O2CMe)(4)](3)[M-III(CN)(6)] [M = Cr (1a),
Fe (2), Co (3)]
were prepared in aqueous solution. Powder X-ray diffraction
indicates
that they have body-centered cubic structures (space group
= lm (3)
over barm, a = 13.34, 13.30, and 13.10 Angstrom for 1a,
2, and 3,
respectively), which was confirmed for 1a by Reitveld
analysis of the
synchrotron powder data [a = 13.3756(5) Angstrom].
[Ru-2(O2CMe)(4)](3)[M-III(CN)(6)](.)xMeCN [M = Cr, x =
1.8 (1b); M =
Mn, x = 3.3 (4)] were prepared from acetonitrile. The
magnetic ordering
of 1a (33 K), 1b (34.5 K), 2 (2.1 K), and 4 (9.6 K) was
determined from
the temperature dependencies of the in-phase (chi') alternating
current
(AC) susceptibility. The field dependence of the magnetization,
M(H),
at 2 K for 1a showed an unusual constricted hysteresis
loop with a
coercive field, H-cr, of 470 Oe while the 10(h) data for
1b, 2, and 4
showed a normal hysteresis loop with a coercive field
of 1670, 10, and
990 Oe, respectively. The Fe-57 Mossbauer spectrum of
2 is consistent
with the presence of low spin Fe-III (6 = -0.05 mm/s;
DeltaE = 0.33
mm/s) at room temperature, and the onset of 3-D magnetic
ordering at
lower temperature (<2 K). The effects of M-III in [M-III(CN)(6)](3-),
and the large zero-field splitting (D) of diruthenium
tetracarboxylates
are discussed. The increasing critical temperatures T-c,
with
increasing S could not be accounted for by mean field
models without
significantly different J values for 1a, 4, and 2. By
fitting the T-c
data with mean field models [H = -2JS(Ru)(.)S(M) - mu(B)(g(Ru)S(Ru)
+
g(M)S(M))(H)], J/k(B) are 4.46, 1.90, and 0.70 K for 1a,
4, and 2,
respectively.
2004-167
Mazina, OS Rybakov, VB Chernyshev, VV
Babaev, EV Aslanov, LA
X-ray mapping in heterocyclic design: XIV. Tricyclic heterocycles based
on 2-oxo-1,2,5,6,7,8-hexahydroquinoline-3-carbonitrile
CRYSTALLOGRAPHY REPORTS 49, 2004, 998-1009.
The structures of four compounds are studied using single-crystal X-ray
diffraction:
1-[2-(4-chlorophenyl)-2-oxoethyl]-2-oxo-1,2,5,6,7,8-hexahydroquinoline-3
-carbonitrile [a = 4.908(4) Angstrom, b = 11.644(10) Angstrom,
c =
13.587(2) Angstrom, beta = 94.31(5)degrees, Z = 2, space
group P2(1)];
2-[2-(4-chlorophenyl)-2-oxoethoxy]-5,6,7,8-tetrahydroquinoline-3-carboni
trile [a = 7.6142(8) Angstrom, b = 14.778(2) Angstrom,
c = 14.132(2)
Angstrom, beta = 100.38(1)degrees, Z = 4, space group
P2(1)/c];
4-(aminocarbonyl)-2-(chlorophenyl)-6,7,8,9-tetrahydro[1.3]oxazolo[3,2-a]
quinolin-3-ium perchlorate [a = 5.589(7) Angstrom, b =
24.724(15)
Angstrom, c = 13.727(5) Angstrom, beta = 97.66(9)degrees,
Z = 4, space
group P2(1)/n]; and
(3-amino-5,6,7,8-tetrahydrofuro[2,3-b]quinolin-2-yl)-(4-chlorophenyl)
methanone [a = 7.150(2) Angstrom, b = 7.4288(10) Angstrom,
c =
15.314(3) Angstrom, alpha. = 98.030(10)degrees, 99.21(2)degrees,
gamma
= 105.34(2)degrees, Z = 2, space group P (1) over bar].
The structures
are solved by direct methods and refined by the full-matrix
least-squares procedure in the anisotropic approximation
to R = 0.0728,
0.0439, 0.1228., and 0.0541, respectively. The structure
of
1-(4-chlorophenyl)-4-piperidin-1-yl-8,9-dihydro-7H-pyrrolo[3.2.1-ij]quin
oline-5-carboxamide [a = 23.9895(9) Angstrom, b = 5.1557(3)
Angstrom, c
= 17.0959(9) Angstrom, 0 = 106.43degrees, Z = 4, space
group P-1/c] is
investigated by X-ray powder diffraction. This structure
is solved
using the grid search procedure and refined by the Rietveld
method to
R-wp = 0.0773, R-exp= 0.0540, R-p = 0.0585, R-b = 0.1107,
and chi(2) =
1.78.
2004-168
Al'bov, DV Mazina, OS Rybakov, VB
Babaev, EV Chernyshev, VV Astanov, LA
X-ray mapping in heterocyclic design: XII. X-ray diffraction study
of
2-pyridones containing cycloalkane fragments annelated
to the C(5)-C(6)
bond
CRYSTALLOGRAPHY REPORTS 49, 2004, 158-168.
The structures of 4,6-dimethyl-1H-pyridin-2-one [a = 6.125(2) Angstrom,
b = 15.153(4) Angstrom, and c = 14.477(4) Angstrom, Z
= 8, space group
Pbca], the 2 : 1 : 1 complex of
4-methyl-1,5,6,7-tetrahydro-2H-cyclopenta[b]pyridin-2-one
with
phosphoric acid and methanol [a = 11.181(2) Angstrom,
b = 14.059'(6)
Angstrom, c = 13.593(4) Angstrom, beta = 97.78(2)degrees,
Z = 8, space
group P2(1)/n],
4-methyl-1,5,6,7,8,9-hexahydro-2H-cyclohepta[b]pyridin-2-one
[a =
12.565(6) Angstrom, b = 5.836(6) Angstrom, c = 13.007(3)
Angstrom, beta
= 93.10(3)degrees, Z = 4, space group P2(1)/n], and
4-methyl-5,6,7,8,9,10-hexahydrocycloocta[b]pyridin-2(1H)-one
[a =
12.955(3) Angstrom, b = 6.1595(15) Angstrom, c = 13.038(3)
Angstrom,
beta = 95.50(2)degrees, Z= 4, space group P2(1)/n] are
determined b
single-crystal X-ray diffraction. The structures are solved
by direct
methods and refined by the full-matrix least-squares procedure
in the
anisotropic approximation to R = 0.0755, 0.0644, 0.0754,
and 0.0569,
respectively. The structures of 4-methyl-
1,5,6,7-tetrahydro-2H-cyclopenta[b]pyridin-2-one [a =
7.353(4)
Angstrom, h = 8.176(4) Angstrom, c = 13.00(1) Angstrom,
beta =
195.64(2)degrees, Z = 4, space group P2(1)/c] and
2-oxo-1,2,5,6,7,8-hexahydroquinoline-3-carbonitrile [a
= 5.9870(2)
Angstrom, b = 16.5280(5) Angstrom, c = 9.6540(3) Angstrom,
beta =
111.52(4)degrees, Z = 4, space group P2(1)/c] are studied
by the powder
diffraction technique. The structures are solved using
the grid search
procedure and refined by the Rietveld method to R-wp =
0. 108 and 0.058
R-exp = 0.032 and 0.027, R-p = 0.076 and 0.043, R-b =
0. 123 and 0.077,
and chi(2) = 7.9 and 3.64, respectively. In all the structures,
hydrogen bonds involving the N, H, and 0 atoms of the
pyridone fragment
are formed.
2004-169
Bouznik, VM Kirik, SD Solovyov, LA
Tsvetnikov, AK
A crystal structure of ultra-dispersed form of polytetrafluoroethylene
based on X-ray powder diffraction data
POWDER DIFFRACTION, 19, 2004, 219-224.
An X-Ray powder diffraction study of ultra-dispersed
polytetrafluoroethylene was carried out. As well as a
regular
polytetrafluoroethylene the ultra-dispersed form contents
a high
proportion of the crystalline phase. The X-ray diffraction
pattern
could be described with two-dimensional hexagonal unit
cell [a
=5.685(i) angstrom, symmetry group p6mm]. Structural modeling
with a
continuous electron density approach as well as with a
discrete
disordered atoms distribution was accomplished. The model
was refined
using the Rietveld method. The structure is characterized
by a spiral
arrangement of polymers (CF2-)(n) along the z-axis with
complete mutual
disordering by rotational displacement around z, as well
as a partial
molecular translation along the z-axis. Molecular disordering
results
in a systematic absence of reflections with 1 not equal
0 and as a
sequence in two-dimensional unit cell effect. The presence
of complete
rotational disordering distinguishes the ultra-dispersed
form of
polytetrafluoroethylene from the standard one (fluoroplast-4),
where
only partial disordering is observed.
2004-170
Muccini, M Loi, MA Kenevey, K Zamboni,
R Masciocchi, N Sironi, A
Blue luminescence of facial tris(quinolin-8-olato)aluminum(III) in
solution, crystals, and thin films
ADVANCED MATERIALS 16, 2004, 861-864.
2004-171
Barea, E Navarro, JAR Salas, JM
Masciocchi, N Galli, S Sironi, A
Mineralomimetic sodalite- and muscovite-type coordination frameworks.
Dynamic crystal-to-crystal interconversion processes sensitive
to ion
pair recognition
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 126, 2004, 3014-3015.
2004-172
Bonnet, PA van de Streek, J Trask, AV
Motherwell, WDS Jones, W
The crystal structure of an unstable polymorph of beta-D-allose
CRYSTENGCOMM 6, 2004, 535-539.
The crystal structure of a new polymorph, Form II, of beta-D-allose
has
been determined by X-ray powder diffraction. The unit
cell is
hexagonal, a = b = 16.598 Angstrom, c = 4.856 Angstrom,
alpha = beta =
90degrees, gamma = 120degrees, space group P6(2) with
Z = 6, Z' = 1.
The molecule adopts the C-4(1) chair-conformation, with
a torsional
change of conformation of the O6 side-chain compared to
the
orthorhombic Form I. The two polymorphs share a common
feature of a
stacked hydrogen bonded column of molecules in the short
axis
direction. The structures differ in hydrogen linking of
these columns.
The more stable Form I has more immediate neighbours linked
by hydrogen
bonds to a reference molecule, and higher crystal density
than Form II.