2003-1
Keller, HL Wimbert, L
On coinage metal mercury chalcogenide halides. III. On the crystal
structure of Ag2HgSI2
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 629, 2003, 2337-2340.
Ag2HgSI2, was obtained as a yellow powder by heating a mixture of AgI
and alpha-HgS at 120degreesC. The compound crystallizes
in space group
type Cmc2(1) with a = 1384.35(6) pm, b = 746.97(3) pm,
c = 710.29(3) pm
and Z = 4. The structure consists of a distorted hexagonal
closed
package of sulphur and iodine, in which a third of the
tetrahedral
spaces is occupied by silver and a third of the octahedral
spaces is
occupied by mercury. The distortion of the hexagonal structure
is
caused by the need of space of the lone pairs at sulphur
and iodine.
This was shown by the calculation of the electron localisation
function (ELF).
TREOR
2003-2 ??
Petrova, SA Mar'evich, VP Zakharov, RG
Selivanov, EN Chumarev, VM Udoeva, LY
Crystal structure of zinc calcium oxysulfide
DOKLADY CHEMISTRY 393, 2003, 255-258.
TREOR
2003-3
Pompetzki, M Dinnebier, RE Jansen, M
Sodium dithiophosphate(V): Crystal structure, sodium ionic conductivity
and dismutation
SOLID STATE SCIENCES 5, 2003, 1439-1444.
Na3PO2S2 was synthesized from the corresponding undecahydrate by
freeze-drying. It dismutates at temperatures above 350
C into Na3PO3S
and Na3POS3. The crystal structure of Na3PO2S2 was determined
from
X-ray powder diffraction data, and refined using the Rietveld
technique
(Pbca, a = 17.5359(2) Angstrom, b = 11.3044(1) Angstrom,
c = 5.8656(1)
Angstrom, R-F2 = 8.45%, R-p = 4.80%, R-wp = 6.79%). The
baricenters of
the PO2S2-tetrahedra are arranged in the sense of a hexagonal
close
packing. One of the P-O bonds of these tetrahedra is oriented
parallel
to the crystallographic c-axis with the POS2-groups in
an eclipsed
mutual orientation. The crystal structure of Na3PO2S2
displays a close
relationship to the ones of Ca3CrN3 and Na3POS3. Above
330 degreesC,
Na3PO2S2 can be regarded as a fast ionic conductor (with
sigma > 10(-5)
S cm(-1)).
TREOR
2003-4
Fukuda, K Fukutani, K
Crystal structure of calcium zirconium diorthophosphate, CaZr(PO4)(2)
POWDER DIFFRACTION 18, 2003, 296-300.
The crystal structure of CaZr(PO4)(2) was determined from conventional
X-ray powder diffraction data using direct methods, and
it was further
refined by the Rietveld method. The structure was orthorhombic
(space
group P2(1)2(1)2(1), Z = 4) with a = 1.44876(4), b = 0.67213(1),
c =
0.62347(2) nm, and V = 0.60710(3) nm(3). Final reliability
indices were
R-wp = 6.49%, R-B = 2.43%, and S = 1.32. The Ca atom is
sevenfold
coordinated, and the Ca atom and surrounding oxygen atoms
form a
distorted capped octahedron with a mean Ca-O distance
of 0.243 nm. The
ZrO7 coordination polyhedron is a distorted pentagonal
bipyramid with a
mean Zr-O distance of 0.216 nm. CaO7, ZrO7, and PO4 polyhedra
share
edges to form infinite chains with the composition
[CaO(3)ZrO(3)p(2)O(8)](12-) along the [010]. Individual
chains are
linked together, forming a two-dimensional sheet parallel
to (100).
These sheets are stacked in the [100] direction to form
a
three-dimensional structure.
TREOR
2003-5
Ferreira, A Lin, Z Soares, MR Rocha,
J
Ab initio structure determination of novel small-pore metal-silicates:
knots-and-crosses structures
INORGANICA CHIMICA ACTA 356, 2003, 19-26.
Sodium chloride stannosilicate AV-13 (Na2.26SnSi3O9Cl0.26.xH(2)O) and
zirconium and hafnium analogues of this material have
been prepared and
their structures solved from powder X-ray diffraction
data using direct
methods, and Na-23, Si-29 and Sn-119 solid-state NMR.
AV-13 materials
are small-pore solids, probably more adequately described
as tunnel
structures. The AV-13 framework consists of corner-sharing
MO6 (M = Sn,
Zr, Rf) octahedra and SiO4 tetrahedra. The latter form
six-membered
[Si6O18](12-) rings, which are interconnected by MO6 octahedra.
The
structure is better understood by considering a three-dimensional
knots- and-crosses lattice. In a given layer, successive
distorted-cube
M-8 cages contain [Na6-x(H2O)](H2O,Cl-) octahedra (knots)
and
cyclohexasilicate (crosses) units. While the former are
extra-framework
species, the six-membered rings are, of course, part of
the framework.
The cages are accessed via seven-membered [M3Si4O27](26-)
windows, with
free aperture ca. 2.3 x 3.2 Angstrom, one per each pseudo-cube
face.
Pilling up layers generates the structure, with knots-and-crosses
alternating. The non-framework five-coordinated Na cations
are
disordered.
TREOR
2003-6
Burton, A Elomari, S Chen, CY Medrud,
RC Chan, IY Bull, LM
Kibby, C Harris, TV Zones, SI
Vittoratos, ES
SSZ-53 and SSZ-59: Two novel extra-large pore zeolites
CHEMISTRY-A EUROPEAN JOURNAL 9, 2003, 5737-5748.
The syntheses, structure solutions, and physicochemical and catalytic
characterizations of the novel zeolites SSZ-53 and SSZ-59
are
described. SSZ-53 and SSZ-59 were synthesized under hydrothermal
conditions with the [1-(4-fluorophenyl)cyclopentylmethyl]trimethyl
ammonium cation and 1-[1-(4-chlorophenyl)cyclopentylmethyl]-1-methyl
azocanium cation, respectively, as structure-directing
agents. The
framework topology of SSZ-53 was solved with the FOCUS
method, and the
structure of SSZ-59 was determined by model building.
Rietveld
refinement of synchrotron X-ray powder diffraction data
confirms each
proposed model. SSZ-53 and SSZ-59 each possess a one-dimensional
channel system delimited by 14-membered rings. Results
from
transmission electron microscopy, electron diffraction,
catalytic
experiments (spaciousness index and constraint index tests),
and argon
and hydrocarbon adsorption experiments are consistent
with the proposed
structures.
TREOR
2003-7
Ferreira, A Ananias, D Carlos, LD
Morais, CM Rocha, J
Novel microporous lanthanide silicates with tobermorite-like structure
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125, 2003, 14573-14579.
The synthesis and structural characterization of microporous lanthanide
silicates (Na(1.08)K(0.5)Ln(1.14-)Si(3)O(8.5).1.78H(2)O,
Ln = Eu, Tb,
Sm, Ce) are reported. The structure of these solids is
closely related
with the structure of hydrated calcium silicate minerals
known as
tobermorites and was solved by powder X-ray diffraction
ab initio
(direct) methods and further characterized by chemical
analysis,
thermogravimetry, scanning electron microscopy, Na-23
and Si-29 MAS NMR
and luminescence spectroscopy. These materials combine
microporosity
with interesting photoluminescence properties, and their
structural
flexibility allows fine-tuning of luminescence properties,
by
introducing a second type of lanthanide ion in the framework.
Thus,
they may find applications in new types of sensors.
TREOR, DICVOL,
2003-8
Zavalij, PY Yang, SF Whittingham, MS
Structures of potassium, sodium and lithium bis(oxalato)borate salts
from powder diffraction data
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 59, 2003, 753-759.
The crystal structures of the alkali-metal bis(oxalato) borate salts
A[B(C2O4)(2)] (A = K, Na, Li) have been determined ab
initio using
powder diffraction data obtained from a laboratory diffractometer.
The
K compound crystallizes in the orthorhombic space group
Cmcm and its
structure has been solved by direct methods applied to
the integrated
intensities from full pattern decomposition. The Na compound
is
isostructural with the K salt, while the crystal structure
of the
highly hydroscopic Li compound differs from the other
two. It has an
orthorhombic lattice, space group Pnma, and its structure
was solved by
the global optimization method using a parallel tempering
approach. In
the K and Na structures the metal ions and complex borate
ions form
chains with m2m symmetry. Metal - oxygen bonding between
the chains
links them into a layer and then a framework with square
tunnels. The
coordination number of both K and Na is eight. The Li
compound also
contains chains that have. m. symmetry and are bound together
into a
three-dimensional framework. The coordination polyhedron
of the Li atom
is a square pyramid with Li lying in its base. This square
pyramidal
coordination leads to its high reactivity with moisture
to give
Li[B(C2O4)(2)] H2O with lithium in six coordination.
TREOR
2003-9
Chernyshev, VV Machon, D Fitch, AN
Zaitsev, SA Yatsenko, AV
Shmakov, AN Weber, HP
Protonation site and hydrogen bonding in anhydrous and hydrated
crystalline forms of doxazosin mesylate from powder data
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 59, 2003, 787-793.
The three-dimensional solid-state structures of two modifications of
doxazosin mesylate C23H26N5O5+.CH3SO3-, 4-amino-2-[
4-[(2,3-dihydro-1,4-benzodioxin-2-yl) carbonyl] piperazin-1-yl]-
6,7-dimethoxyquinazoline methanesulfonate, a commonly
used
antihypertensive agent, have been determined by synchrotron
X-ray
powder diffraction. An anhydrous form (A) and a dihydrate
form (dG)
crystallize in monoclinic space groups. In both forms
the doxazosin
molecule is protonated at the N1 atom of the quinazoline
bicycle. The
N1 atom, and the amino H atoms and O atoms of the mesylate
moieties are
involved in three-dimensional hydrogen-bonding networks,
while solvent
water molecules and carboxamide O atoms are also incorporated
in a
hydrogen-bonding network in dG.
TREOR
2003-10
Miura, H Ushio, T Nagai, K Fujimoto,
D Lepp, Z Takahashi, H Tamura, R
Crystallization of a desired metastable polymorph by pseudoseeding,
crystal structure solution from its powder X-ray diffraction
data, and
confirmation of polymorphic transition
CRYSTAL GROWTH & DESIGN 3, 2003, 959-965.
Described are the successful, selective crystallization and
characterization of one (delta-form) of the metastable
polymorphs of
(+/-)-[2-[4-(3-ethoxy-2-hydroxypropoxy)phenylcarbamoyl]ethyl]dimethylsul
fonium p-toluenesulfonate (1a), which is assumed to exist
as a
transient key-intermediate crystalline phase relevant
to the mechanism
of Preferential Enrichment, an unusual enantiomeric resolution
phenomenon observed upon crystallization of a certain
kind of racemates
from solvents. By pseudoseeding the supersaturated solution
with the
delta-form seed crystals of an anlogous compound, the
desired
delta-form crystals of (+/-)-1a could be obtained as a
monophasic
powder sample. This selective crystallization can be interpreted
in
terms of the interplay between an inhibition of the nucleation
or
crystal growth process of the undesired stable alpha-polymorphic
form
and a heterogeneous nucleation of the desired metastable
delta-form
through epitaxy. The physicochemical properties of the
delta-form.
crystal such as melting point and solubility have been
compared with
those of the stable alpha-form one to evaluate the relative
stability
of the metastable delta-form. It has also been confirmed
that
polymorphic transition of the metastable delta-form crystal
to the
stable alpha-form one occurs in contact with a solvent.
On the basis of
the delta-form crystal structure solved from its powder
X-ray
diffraction data measured with a laboratory X-ray source
by means of
the direct-space approach employing the Monte Carlo method
and the
subsequent Rietveld refinement, the origin of the metastability
of the
delta-form crystal has been discussed.
2003-11
Fujimoto, D Tamura, R Lepp, Z Takahashi,
H Ushio, T
Mechanism of a new type of solvent-assisted solid-to-solid polymorphic
transition causing preferential enrichment: Prominent
influence of
C(sp(2))H ...O interaction on the control of a crystal
structure
CRYSTAL GROWTH & DESIGN 3, 2003, 973-979.
A new mode of the solvent-assisted solid-to-solid transformation of
the
first-formed and least stable gamma-polymorphic form into
the most
stable epsilon-polymorphic one occurring during crystallization
from
the supersaturated EtOH solution of
(+/-)-[2-[4-(3-ethoxy-2-hydroxypropoxy)phenylcarbamoyl]ethyl]trimethylam
monium benzenesulfonate [(+/-)-2], which shows an unusual
enantiomeric
resolution phenomenon called Preferential Enrichment,
has been
revealed. The crystal structure of the new epsilon-form,
which was
obtained as the monophasic powder sample by exhaustive
polymorphic
transitions via three other metastable polymorphic forms
in contact
with the solvent, has been solved from the powder X-ray
diffraction
data by the direct-space approach employing the Monte
Carlo method with
the subsequent Rietveld refinement. By comparison of the
crystal
structure of the least stable gamma-form with that of
the most stable
epsilon-one, the mechanism of this polymorphic transition
has been
interpreted in terms of a new type of rearrangement of
weak
intermolecular interactions caused by a slight molecular
movement
inside the crystal lattice, in which intermolecular C(sp(2))H...O
interactions prominently control the crystal structure.
This new
finding complements our recent report on the mechamisn
of Preferential
Enrichment.
TREOR
2003-12
Montejo-Bernardo, JM Garcia-Granda, S Bayod-Jasanada,
MS Llavona-Diaz, L Llorente, I
X-ray study of the pseudopolymorphism of the azithromycin monohydrate
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 218, 2003, 703-707.
A combination of X-ray powder diffraction and single crystal studies
on
azithomycin pseudopolymorphs give the precise solid state
composition
of all monohydrate pseudopolymorphs reported. According
to the X-ray
results the four monohydrates of azithromycin studied
have the same
crystallographic parameters. Furthermore, the analysis
of the relative
intensities from the powder patterns points to very similar
chemical
compositions and crystal structures. This result has been
confirmed by
the single crystal studies. The single crystal studies
show that the
solid state conformation of the azithromycin molecules
is affected by
the presence of solvents. The solvent methanol molecules
were found
disordered probably due to the existence of many positions
where the
hydrogen bonding is favoured and the large size of the
available space
to host the solvents.
TREOR
2003-13
Cheung, EY Harris, KDM Johnston, RL
Hadden, KL Zakrzewsk, M
Polymorphism of a novel sodium ion channel blocker
JOURNAL OF PHARMACEUTICAL SCIENCES 92, 2003, 2017-2026.
2-{[4-(4-Fluorophenoxy)phenyl]-methylene}-hydrazinecarboxamide,a member
of the semicarbazone family which has shown potential
therapeutic use
as anticonvulsants, has been found to exist in two polymorphic
forms
denoted A and B. In addition to reporting aspects of the
physical
characterization of both forms, the crystal structure
of polymorph A
has been determined directly from powder X-ray diffraction
data using
the Genetic Algorithm technique for structure solution,
followed by
Rietveld refinement. This structure is compared with that
of polymorph
B, which was determined previously from single crystal
X-ray
diffraction data. Knowledge of the crystal structures
of the two
polymorphs provides the opportunity for establishing structure-property
relationships. This work further emphasizes the scope
and utility of ab
initio structure solution from powder X-ray diffraction
data in the
pharmaceuticals field.
TREOR
2003-14 - failed... ??
Masciocchi, N Castelli, F Forster, PM
Tafoya, MM Cheetham, AK
Synthesis and characterization of two polymorphic crystalline phases
and an amorphous powder of nickel(II) bisimidazolate
INORGANIC CHEMISTRY 42, 2003, 6147-6152.
Nickel(II) bisimidazolate is polymorphic. Depending on the synthetic
strategy adopted, two crystalline phases (alpha- and beta-Ni(im)(2))
or
an amorphous material of the same composition can be prepared.
The
thermodynamically stable alpha-Ni(im)(2) phase, which
can be prepared
in water at elevated temperatures, contains a two-dimensional
polymer
(of nearly square meshes) with square-planar NiN4 chromophores
and
exo-bidentate imidazolate ligands bridging nickel atoms
that are ca.
5.73 Angstrom apart. The beta-Ni(im)(2) Phase can be kinetically
stabilized at lower temperatures, but the structural complexity
and the
lack of single crystals prevented its full structural
characterization,
even in the presence of an indexed powder diffraction
pattern. The
spectroscopic features of these crystalline phases are
compared with
those of the amorphous material.
TREOR
2003-15
Le Bail, A Stephens, PW Hubert, F
A crystal structure for the souzalite/gormanite series from synchrotron
powder diffraction data
EUROPEAN JOURNAL OF MINERALOGY 15, 2003, 719-723.
In absence of suitable single crystal due to polysynthetic twinning,
the crystal structure of a specimen in the souzalite/gormanite
series
(Fe,Mg)(3)(Al,Fe)(4)(PO4)(4)(OH)(6).2H(2)O is determined
ab initio from
synchrotron powder diffraction data. The crystals belong
to space group
P (1) over bar, the cell is different from previously
reported with
a=7.2223(1), b=11.7801(1), c=5.1169(1) Angstrom; alpha=90.158(1),
beta=109.938(1), gamma=81.330(1)degrees; V=404.02(1) Angstrom(3);
Z=1.
The structure consists of infinite chains of alternating
[FeO6], [MgO6]
and [AlO6] octahedra sharing faces and/or edges. These
chains are
connected by corners with clusters of three corner-sharing
[AlO6]
octahedra, forming octahedral layers which are interconnected
by [PO4]
groups. A comparison with other minerals of similar composition
and
structure is made (dufrenite, burangaite).
TREOR, DICVOL
2003-16
Tafeenko, VA Chernyshev, VV Yatsenko, AV
Makarov, VA Sonneveld, EJ
Peschar, R Schenk, H
Intermolecular -CH3 . . . O2N-contacts
in
two polymorphic modifications of (1E)-N
'-[(E)-2-cyano-1-(dimethylamino)-2-nitrovinyl]-N,N-dimethylethanimidamide
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 59, 2003, 492-497.
The title compound was synthesized and isolated in two crystal
modifications. The structure of the orthorhombic modification
was
determined by the X-ray powder diffraction method and
the structure of
the monoclinic modification was determined using the X-ray
single-crystal diffraction technique. The molecules in
both polymorphs
are E, E isomers. Intermolecular H3C...NO2 contacts and
their role in
the formation of the polymorphic modifications are analyzed.
TREOR
2003-17
Masciocchi, N Ardizzoia, GA Brenna, S
Castelli, F Galli, S
Maspero, A Sironi, A
Synthesis and ab-initio XRPD structure of group 12 imidazolato polymers
CHEMICAL COMMUNICATIONS iss 10, 2003, 2018-2019.
Two new 3D homoleptic binary imidazolates, Cd(im)(2) and Hg(im)(2)
(Him
= imidazole), as well as [Hg(im)]NO3, containing 1D polycations
of
[Hg(im)](n)(n+) formulation, have been prepared and characterized
by
ab-initio XRPD methods.
TREOR
2003-18
Ivashkevich, LS Lyakhov, AS Selevich, AF
Petrusevich, YI
The crystal structure of Er(HPO4)(NO3) . 3 H2O: ab initio
determination from X-ray powder diffraction data
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 218, 2003, 475-479.
The crystal structure of orthorhombic Er(HPO4)(NO3) . 3 H2O has been
determined from X-ray powder diffraction data. The unit
cell dimensions
are a = 10.1653(4) Angstrom, b = 11.9178(5) Angstrom,
c = 6.8533(3)
Angstrom, V = 830.26(6), Z = 4. The space group is Pbcm
(No. 57) or
Pbc2(1) (No. 29). The structures were solved ab initio
using EXPO
program and refined by FULLPROF package.
Because geometrical features of the two solutions are
the same, the
crystal structure has been described in the scope of the
centrosymmetric Pbcm space group. Positions of the hydrogen
atoms were
not defined. The erbium atom is eight coordinated. It
is surrounded by
one nitrate anion, one water molecule and four phosphate
groups. [ErO8]
polyhedra are linked together through their edges forming
infinite
chains extended along the c axis. The chains are connected
by phosphate
groups to form layers palallel to the yz plane. Probable
hydrogen bonds
are discussed.
TREOR
2003-19
Nowell, H Shan, N Attfield, JP Jones,
W Motherwell, WDS
The structure of cyclohexane-1, 3cis, 5cis-tricarboxylic acid,
determined from powder X-ray diffraction data
CRYSTAL ENGINEERING 6, 2003, 57-67.
The previously unknown crystal structure of cyclohexane-1, 3cis,
5cis-tricarboxylic acid (CTA) has been solved from laboratory
X-ray
powder diffraction data using a simulated annealing algorithm
followed
by restrained Rietveld refinement (reduced-chi(2) = 8.531
for the
refined crystal structure). The structure is triclinic
(P (1) over bar,
Z = 4). Five out of six of the CO2H groups in the asymmetric
unit form
R-2(2)(8) hydrogen bond motifs with neighbouring CO2H
groups. The
motifs connect molecules to form pseudo-hexagonal, ten-molecule
rings
that fuse into supramolecular buckled honeycomb sheets,
which stack and
are linked by O-(HO)-O-... hydrogen bonds.
TREOR
2003-20
Masciocchi, N Brenna, S Galli, S
Maspero, A
Ab-initio XRPD structural characterization of coordination polymers:
the case of [Ag(C3H3N2CS2)]
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 218, 2003, 450-454.
The crystal structure of the one-dimensional polymer [Ag(C3H3N2CS2)]
has been determined from conventional X-ray powder diffraction
methods,
through simulated annealing and Rietveld refinement techniques
[Ag(C3H3N2CS2)] is monoclinic, P2(1)/c; a = 8.409(l),
b = 11.740(l), c
= 6.721(l) Angstrom, beta = 101.86(2)degrees, V = 649.3(2)
Angstrom(3);
Z = 4; rho = 2.566 g cm(-3) Final R-wp, R-p and R-F agreement
factors,
for 3 100 data points collected in the 8-70degrees 2theta
range, are
0.091, 0.071 and 0.058, respectively. Anisotropic peak
shapes and
high-angle tails for the 0k0 (and neighboring) reflections
suggest that
the polymeric chains, aligned along b, suffer from a partial
disorder,
in that packing of adjacent molecules does not conform
to a rigorous
crystalline, truly periodic, tiling.
TREOR
2003-21
Ivashevskaja, SN Aleshina, LA Andreev,
VP Nizhnik, YP
Chernyshev, VV Schenk, H
4-(4 '-dimethylaminostyryl)pyridine N-oxide from powder data
ACTA CRYSTALLOGRAPHICA SECTION E-STRUCTURE REPORTS ONLINE 59, 2003,
O1006-O1008
The crystal structure of 4-(4-dimethylaminophenylethenyl)pyridine
N-oxide, C15H16N2O, has been determined from X-ray laboratory
powder
diffraction data. The powder pattern was indexed with
a monoclinic unit
cell with a long a axis. The structure was solved by a
grid search
technique. The subsequent bond-restrained Rietveld refinement
gave bond
lengths and angles within expected ranges.
TREOR
2003-22
Grzechnik, A Bouvier, P Farina, L
High-pressure structure of Li2CO3
JOURNAL OF SOLID STATE CHEMISTRY 173, 2003, 13-19.
The high-pressure behavior of Li2CO3 is studied up to 25 GPa with
synchrotron angle-dispersive powder X-ray diffraction
in diamond anvil
cells and synthesis using a multi-anvil apparatus. A new
non-quenchable
hexagonal polymorph (P6(3)/mcm, Z = 2) occurs above 10
GPa with
carbonate groups in a staggered configuration along the
c-axis-a =
4.4568(2) Angstrom and c = 5.1254(6) Angstrom at 10 GPa.
Two columns of
face-shared distorted octahedra around the Li atoms are
linked through
octahedral edges. The oxygen atoms are coordinated to
one carbon atom
and four lithium atoms to form a distorted square pyramid.
Splittings
of X-ray reflections for the new polymorph observed above
about 22 GPa
under non-hydrostatic conditions arise from orthorhombic
or monoclinic
distortions of the hexagonal lattice. The results of this
study are
discussed in relation to the structural features found
in other Me2CO3
carbonates (Me: Na, K, Rb, Cs) at atmospheric conditions.
TREOR
2003-23
Le Bail, A Mercier, AM
Distorted chiolite crystal structures of alpha-Na5M3F14 (M=Cr,Fe,Ga)
studied by X-ray powder diffraction
POWDER DIFFRACTION 18, 2003, 128-134.
The crystal structures of the chiolite-related room temperature phases
alpha-Na5M3F14 (M-III =Cr,Fe,Ga) are determined. For all
of them, the
space group is P2(1)/n, Z=2; a= 10.5096(3) Angstrom, b=7.2253(2)
Angstrom, c=7.2713(2) Angstrom, beta=90.6753(7)degrees
(M = Cr); a=
10.4342(7) Angstrom, b = 7.3418(6) Angstrom, c = 7.4023(6)
Angstrom,
beta=90.799(5)degrees (M = Fe), and a= 10.4052(1) Angstrom,
b=7.2251(1)
Angstrom, c=7.2689(1) Angstrom, beta=90.6640(4)degrees
(M = Ga).
Rietveld refinements produce final R-F factors 0.036,
0.033, and 0.035,
and R-WP factors, 0.125, 0.116, and 0.096, for M-III=Cr,
Fe, and Ga,
respectively. The MF6 polyhedra in the defective isolated
perovskite-like layers deviate very few from perfect octahedra.
Subtle
octahedra tiltings lead to the symmetry decrease from
the P-4/mnc space
group adopted by the Na5Al3F14 chiolite aristotype to
the P2(1) In
space group adopted by the title series. Facile twinning
precluded till
now the precise characterization of these compounds.
2003-24
Crichton, WA Mezouar, M Monaco, G
Falconi, S
Phosphorus: New in situ powder data from large-volume apparatus
POWDER DIFFRACTION 18, 2003, 155-158.
Improved X-ray powder diffraction data for orthorhombic phosphorus,
S.G. Cmca (64) obtained in situ at synthesis conditions
of 1.2 GPa and
1100 K, are described. Representative, as synthesized,
data include
2.552(X), 3.320(4), 2.595(3), 5.191(2), 1.630(2), for
least-squares
unit-cell a=3.3182(6) Angstrom, b= 10.3744(18) Angstrom
and c=4.3227(9)
Angstrom. As an illustration of the quality of the data,
the structure
was solved from powder XRD and Rietveld refined to give
a=3.3199(2)
Angstrom, b= 10.3678(4) Angstrom, c=4.3154(2)Angstrom,
and
V=148.535(12) Angstrom(3) with the P atom on 8f (1/2,
y,z) with
y=0.1044(22) and z=0.9179(7). (C) 2003 International Centre
for
Diffraction Data.
P, Cmca, synchrotron data
CRYSFIRE, ENDEAVOUR, GSAS
2003-25
Grzechnik, A Crichton, WA Gesland, JY
Potassium triyttrium decafluoride, KY3F10, synthesized at high
pressures and high temperatures
SOLID STATE SCIENCES 5, 2003, 757-764.
Potassium triyttrium decafluoride, KY3F10, has been studied at high
pressures and high temperatures using in situ synchrotron
angle-dispersive X-ray powder diffraction in a Paris-Edinburgh
cell and
syntheses in a multi-anvil apparatus. At ambient conditions
this
compound exhibits a 2 x 2 x 2-fluorite superstructure
(Fm (3) over
barm, Z = 8, a = 11.54315(1) Angstrom) with yttrium atoms
displaced
from the ideal fcc positions. Upon compression to above
7.5 GPa at room
temperature, a new polymorph is formed (Pm (3) over barn,
Z = 1, a =
5.70485(8) Angstrom for the sample synthesized at 10.5
GPa and 298 K)
with potassium and yttrium atoms in the ideal fluorite
positions.
Fluorine atoms are disordered and split on partially occupied
sites.
The same phase of KY3F10 is obtained at lower pressures
and high
temperatures. This new structure is discussed in relation
to other
fluorite superstructures.
TREOR
2003-26
Masciocchi, N Galli, S Sironi, A
Barea, E Navarro, JAR Salas, JM Tabares,
LC
Rich structural and magnetic chemistry of cobalt(II) pyrimidin-2-olate
and pyrimidin-4-olate complexes. Synthesis, X-ray powder
diffraction
studies, and thermal behavior
CHEMISTRY OF MATERIALS 15, 2003, 2153-2160.
Two new cobalt(II) species containing the pyrimidin-4-olate ligand
(4-pymo) have been prepared and fully characterized by
spectroscopic,
thermal, and ab initio X-ray powder diffraction methods.
The magnetic
properties of both these species and Co(2-pymo)(2), an
extended
cobalt(II) compound containing the pyrimidine-2-olate
ligand (2-pymo),
are also reported. Co(4-pymo)(2)(H2O)(4) (1) [orthorhombic,
Pcab, a =
13.5233(4) Angstrom, b = 12.9617(3) Angstrom, and c =
6.7925(2)
Angstrom] consists of D-4h octahedral monomers, bearing
axial 4-pymo
ligands, interlinked by an extensive network of OH...X
(X = O, N)
hydrogen bonds. Upon heating, it loses water and transforms
into an
amorphous (above 150 degreesC) (2a) or a polycrystalline
above 320
degreesC) Co(4-pymo)(2) phase (2b) [orthorhombic, Imma,
a = 6.5720(8)
Angstrom, b = 6.6209(8) Angstrom, and c = 20.688(2) Angstrom].
In the
latter, C-2v pseudo-tetrahedral cobalt(II) ions are linked
by 4-pymo
ligands in the unusual N,O-exo-bidentate mode, generating
2D layers of
nearly square meshes, thus significantly differing from
the
Co(2-pymo)(2) analogue (3), in which N,N'-exo-bidentate
bridges
generate an acentric, 3D diamondoid network. The thermal
dependence of
the magnetic susceptibility has been studied for all the
above
compounds (1, 2a, 2b, and 3) in the 2-300 K temperature
range. The
magnetic behavior of 1 is dominated by spin-orbit coupling
of
magnetically isolated octahedral Co(II) centers. The extended
materials
2a and 2b show antiferromagnetic exchange between distorted
tetrahedral
metal centers, whereas 3 behaves as a spin-canted antiferromagnet,
a
ferromagnetic ordering taking place below a critical temperature,
T-c =
23 K; 3 can thus be considered as a molecular magnet.
Indeed, magnetic
hysteresis studies on 3 at 4.8 K yield a coercitive field
H-coer = 3900
G and a remnant magnetization M-rem = 279 cm(3) G mol(-1).
TREOR
2003-27
Cecconi, F Dominguez, S Masciocchi, N
Midollini, S Sironi, A Vacca, A
Complexation of beryllium(II) ion by phosphinate ligands in aqueous
solution. Synthesis and XRPD structure determination of
Be[(PhPO2)(2)CH2](H2O)(2)
INORGANIC CHEMISTRY 42, 2003, 2350-2356.
Two bifunctional ligands, phenyl(carboxymethyl)phosphinate (ccp(2-))
and P,P'-diphenylmethylenediphosphinate (pcp(2-)), have
been tested as
chelating agents of beryllium(II). Both ligands have the
same charge
and a similar chelating structure, but whereas the 1:1
adduct of
pcp(2-), Be(pcp)((HO)-O-2)(2), could be isolated as a
white powder, no
pure compound could be isolated from solutions containing
beryllium(II)
and ccp(2-). Instead, the solutions were examined by means
of
potentiometry and Be-9 NMR spectroscopy. Analysis of the
potentiometric
titration data with the program HYPERQUAD suggested the
formation of
the complex species BeL, [BeHL](+), [BeL2](2-), and [BeHL2](-)
(L =
ccp). The formation constants for these species were determined
at 25
degreesC and / = 0.5 mol dm(-3) NaCIO4. The Be-9 NIVIR
spectra are
consistent with this model. The formation constants found
for the
ccp(2-) complexes are lower than those reported for related
phosphonate
ligands. However, the effective stability constant (which
gives a
better indication of the intrinsic coordinating capacity
of the ligand
at a particular pH) of the complex [Be(ccp)(2)](2-) at
pH < 4 is
greater than the effective constants of the corresponding
phosphonoacetate and methylenediphosphonate complexes.
The structure of
Be(pcp)(H2O)(2) was determined by X-ray powder diffraction
methods and
consists of discrete molecules interconnected by an extended
2D network
of hydrogen bonds, resulting in a stacking of double layers
with a
polar core and a lipophilic surface. Crystal data: C13H16BeO6P2,
fw
339.21, monoclinic P2(1)/c, a 16.174(1) Angstrom, b =
8.979(1)
Angstrom, c = 10.929(1) Angstrom, beta = 90.398(9)degrees,
V =
1587.2(3) Angstrom(3), Z = 4.
TREOR
2003-28
Boullay, P Mercurio, D Bencan, A
Meden, A Drazic, G Kosec, M
An XRPD ab-initio structural determination of La2RuO5
JOURNAL OF SOLID STATE CHEMISTRY 170, 2003, 294-302.
The crystal structure of a new oxide, La2RuO5, was determined ab initio
using conventional laboratory X-ray powder diffraction.
Combining X-ray
and electron diffraction techniques, we found that the
new phase
crystallized in the monoclinic system with the space group
P2(1)/c (SG
no.14) and the cell parameters a 9.1878(2) Angstrom, b=5.8313(2)
Angstrom, c 7.9575(2) Angstrom and beta=100.773(2)degrees
(V=418.8
Angstrom(3), Z=4). The structural determination with the
Patterson
method and Fourier difference syntheses and the final
Rietveld
refinement were performed by means of the JANA2000 program.
The
structure is built up from the regular stacking, of a
two octahedra
thick [LaRuO4](infinity) zigzag perovskite slab and an
original similar
to3.4 Angstrom thick [LaO](infinity) slab which constitutes
the key
feature of this new structure. (C) 2002 Elsevier Science
(USA). All
rights reserved.
TREOR
2003-29
Juarez-Arellano, EA Bucio, L Hernandez, JA
Camarillo, E
Carbonio, RE Orozco, E
Synthesis, crystal structure, and preliminary study of luminescent
properties of InTbGe2O7
JOURNAL OF SOLID STATE CHEMISTRY 170, 2003, 418-423.
A new indium terbium germanate InTbGe2O7, which is a member of the
thortveitite family, was prepared as a polycrystalline
powder material
by high-temperature solid-state reaction. This new compound
crystallizes in the monoclinic system, space group C2/c
(No. 15), with
unit cell parameters a = 6.8818(2)Angstrom, b = 8.8774(3)Angstrom,
c =
9.7892(4)Angstrom, beta = 101.401 (1)degrees V = 586.25(4)Angstrom(3)
and Z = 4. Its structure was characterized by Rietveld
refinement of
powder laboratory X-ray diffraction data. It consists
of octahedral
sheets that are held together by sheets of isolated Ge2O7
diorthogroups
composed of two tetrahedra sharing a common vertex. It
contains only
one octahedral site occupied by In3+ and Tb+3 cations.
The
characteristic mirror plane in the thortveitite (SC2Si2O7)
space group
(C2/m, No. 12) is not present in this new compound. Besides,
in
InTbGe2O7, the Ge-O-Ge angle bridging two diorthogroups
is
156.8(2)degrees as compared to the one in thortveitite,
which is
180degrees. On the other hand, luminescent properties
were observed
when it is excited with 376.5 nm wavelength. The luminescence
spectrum
shows typical transitions from the D-5(4) multiplet belonging
to the
trivalent terbium ion.
TREOR
2003-30
Hassfjell, S Kongshaug, KO Romming, C
Synthesis, crystal structure and chemical stability of bismuth(III)
complexed with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene
phosphonic acid (H8DOTMP)
DALTON TRANSACTIONS 2003, 1433-1437.
The potential use of the alpha-particle emitting compounds Bi-212/213
-DOTMP and Pb-212-DOTMP in therapy of bone-associated
cancers, and
medical interest in bismuth compounds, motivated this
study. Syntheses
of the Bi(III) and Pb(III) complexes of
1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene
phosphonic acid
(H8DOTMP) are reported. Extensive pH-stability was found
for both
complexes, in the pH range 0-13 for Bi-DOTMP and pH 4-14
for Pb-DOTMP.
Furthermore, both complexes formed within 1 min in the
pH range 6-10 at
10 muM metal-ion and 15 muM DOTMP. Single crystals of
[NaBi(H4DOTMP)]
and polycrystalline [Bi(H5O2)(H4DOTMP)] were formed and
characterized
by single crystal and powder X-ray diffraction methods,
respectively.
The structure of the anion was found in both salts to
exhibit a square
antiprismatic eight-coordination with a four-fold axis
of symmetry.
TREOR
2003-31
Bellitto, C Bauer, EM Ibrahim, SA
Mahmoud, MR Righini, G
Synthesis, X-ray powder structure, and magnetic properties of layered
Ni-II methylphosphonate, [Ni(CH3PO3)(H2O)], and Ni-II
octadecylphosphonate, [Ni{CH3-(CH2)(17)-PO3}(H2O)]
CHEMISTRY-A EUROPEAN JOURNAL 9, 2003, 1324-1331.
[Ni(CH3PO3)(H2O)] (1) and [Ni[CH3-(CH2)(17)-PO3}(H2O)] (2) were
synthesised by reaction of NiCl2 . 6H(2)O and the relevant
phosphonic
acid in water in presence of urea. The compounds were
characterised by
elemental and thermogravimetric analyses, UV-visible and
IR
spectroscopy, and their magnetic properties were studied
by using a
SQUID magnetometer. The crystal structure of I was determined
''ab
initio" from X-ray powder diffraction data and refined
by the Rietveld
method. The crystals of 1 are orthorhombic, space group
Pmn2(1), with a
= 5.587(1), b = 8.698(1), c = 4.731(1) Angstrom. The compound
has a
hybrid, layered structure made up of alternating inorganic
and organic
layers along the b direction of the unit-cell. The inorganic
layers
consist of Ni-II ions octahedrally coordinated by five
phosphonate
oxygen atoms and one oxygen atom from the water molecule.
These layers
are separated by bilayers of methyl groups and van der
Waals contacts
are established between them. A preliminary structure
characterisation
of compound 2 suggests the crystallisation in the orthorhombic
system
with the following unit-cell parameters: a = 5.478(7),
b = 42.31(4), c
= 4.725(3) Angstrom. The oxidation state of the Ni ion
in both
compounds is +2, and the electronic configuration is d(8)
(S = 1), as
determined from static magnetic susceptibility measurements
above 50 K.
Compound 1 obeys the Curie-Weiss law at temperatures above
50 K; the
Curie (C) and Weiss (0) constants were found to be 1.15
cm(3) K mol(-1)
and -32 K, respectively. The negative value of theta indicates
an
antiferromagnetic exchange coupling between near-neighbouring
Ni-II
ions. No sign of 3D antiferromagnetic long-range order
is observed down
to T = 5 K, the lowest measured temperature. Compound
2 is paramagnetic
above T= 50 K, and the values of C and 0 were found to
be 1.25 cm(3) K
mol(-1) and - 24 K, respectively. Below 50 K the magnetic
behavior of 2
is different from that of 1. Zero-field cooled (zfc) and
field-cooled
(fc) magnetisation plots do not overlap below T= 21 K.
The irreversible
magnetisation, DeltaM(fc-zfc), obtained as a difference
from fc and zfc
plots starts to increase at T= 20 K, on lowering the temperature,
and
it becomes steady at T= K. The presence of spontaneous
magnetisation
below T = 20 K indicates a transition to a weak-ferromagnetic
state for
compound 2.
TREOR, N-TREOR
2003-32
Yamada, H Shi, WS Nishikubo, K Xu,
CN
Determination of the crystal structure of spherical particles of
SrAl2O4 : Eu prepared by the spray method
JOURNAL OF THE ELECTROCHEMICAL SOCIETY 150, 2003, E251-E254.
The crystal structure of spherical particles of Sr0.88Eu0.12Al2O4
synthesized by the spray method has been investigated
by powder X-ray
diffraction measurements. After annealing at 1300degreesC
for 2 h, the
spheres of Sr0.88Eu0.12Al2O4 crystallize in the hexagonal
form with a =
5.1160(2) Angstrom, c = 8.3722(3) Angstrom, V = 189.77(1)
Angstrom(3),
Z = 2, and space group P6(3)22, which is distinct from
the structure
(monoclinic P2(1)) reported so far. This stable crystal
structure was
refined by the Rietveld method, and it was found that
it consists of a
nondistorted stuffed tridymite structure, and the doped
Eu2+ ion is
located at the same 2b site as the Sr2+ ion. Furthermore,
it is
suggested that such an abnormal stabilization of the hexagonal
form at
ambient temperature is associated with defects of the
oxygen ion at the
2d site based on the electron density map from Fourier
synthesis.
TREOR
2003-33
Ivashkevich, LS Lyakhov, AS Selevich, AF
Lesnikovich, AI
Ab initio structure determination of In2H2(P2O7)(P4O12))(P4O12) from
X-ray powder diffraction data
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 218, 2003, 32-36.
The crystal structure of In2H2(P2O7)P4O12) has been determined from
X-ray powder diffraction data. The structure is orthorhombic,
space
group Pmmn (No. 59), with unit cell dimensions a = 12.9398(2)
Angstrom,
b = 11.3725(3) Angstrom, c = 5.0385(1) Angstrom, V = 741.45(3)
Angstrom, Z = 2, and D-x = 3.23 g/cm(3). The structure
has been solved
by direct methods using EXPO program and refined by FULLPROF
package.
The final R-Bragg value was 4.6%. Positions of hydrogen
atoms were not
defined. Indium cation has sixfold oxygen coordination
being surrounded
by two diphosphate and four cyclotetraphosphate groups.
Probable scheme
of hydrogen bonding is discussed.
TREOR
2003-34
Simon-Masseron, A Paillaud, JL Patarin, J
Mu-21: A three-dimensional microporous zincophosphate obtained by
direct synthesis and reversible dehydration of the zincophosphate
Mu-19
CHEMISTRY OF MATERIALS 15, 2003, 1000-1005.
A zincophosphate named Mu-21 (Zn4P8O32H12(C5H12NO)(4)) was obtained
in
solvothermal conditions from a ZnO/H3PO4/N-methylmorpholine/ethylene
glycol mixture, and its structure was solved ab initio
from powder
data. Mu-21 crystallized in the orthorhombic space group
P 2(1)2(1)2(1)
with a = 10.4200(1), b = 10.4523(2), c = 11.6221(2) Angstrom,
and V =
1265.80(3) Angstrom(3). Mu-21 was also obtained by reversible
dehydration of the zincophosphate Mu-19 at 80 degreesC.
This material
was characterized by P-31, H-1 MAS NMR, and SEM.
TREOR
2003-35
Kiang, YH Xu, W Kaufman, MJ
Ab initio structure determination of rofecoxib from powder diffraction
data using molecular packing analysis method and direct
space method
INTERNATIONAL JOURNAL OF PHARMACEUTICS 252, 2003, 213-223.
Crystal structures of a COX-II inhibitor, rofecoxib (Vioxx(R)) were
solved ab initio from X-ray powder diffraction pattern
using both
molecular packing analysis and direct space methods. The
X-ray powder
pattern was indexed into a tetragonal cell. Packing energies
were
generated and analyzed in eight most frequently found
tetragonal space
groups. The two space groups with the lowest total energy,
P4(1)2(1)2
and P4(3)2(1)2, were used for direct space method with
a
Monte-Carlo/Simulated Annealing searching algorithm. Structural
solutions obtained from direct space method were evaluated
using
molecular packing energy analysis. The structures solved
ab initio from
this work were compared to the single crystal structure
deposited in
the Cambridge Structural Database.
TREOR
2003-36
Burton, A Elomari, S Medrud, RC
Chan, IY Chen, CY Bull, LM Vittoratos,
ES
The synthesis, characterization, and structure solution of SSZ-58:
A
novel two-dimensional 10-ring pore zeolite with previously
unseen
double 5-ring subunits
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125, 2003, 1633-1642.
The synthesis, structure solution, and characterization of the novel
zeolite SSZ-58 are described. SSZ-58 was synthesized under
hydrothermal
conditions using 1-butyl-1-cyclooctylpyrrolidinium cation
as a
structure-directing agent. The framework topology of SSZ-58
was
determined with the FOCUS Fourier recycling method. SSZ-58
possesses 12
tetrahedral atoms in the asymmetric unit of its highest
topological
symmetry, and to date it is the most complex zeolite structure
solved
from powder data. Rietveld refinement of synchrotron powder
X-ray
diffraction data in space group Pmma confirmed the proposed
model.
SSZ-58 contains layers of atoms that are linked together
by double
five-membered rings (D5R), or 5(2)4(5) subunits, that
have not been
observed before in any zeolite or zeotype structures.
SSZ-58 possesses
a two-dimensional channel system consisting of 10-membered
ring pores
that intersect to form large Cavities circumscribed by
12- and
16-membered ring pores.
TREOR, DICVOL
2003-37
Huq, A Stephens, PW
Subtleties in crystal structure solution from powder diffraction data
using simulated annealing: Ranitidine hydrochloride
JOURNAL OF PHARMACEUTICAL SCIENCES 92, 2003, 244-249.
Recent advances in crystallographic computing and availability of
high-resolution diffraction data have made it relatively
easy to solve
crystal structures from powders that would have traditionally
required
single crystal samples. The success of direct space methods
depends
heavily on starting with an accurate molecular model.
In this paper we
address the applicability of using these methods in finding
subtleties
such as disorder in the molecular conformation that might
not be known
a priori. We use ranitidine HCl as our test sample as
it is known to
have a conformational disorder from single crystal structural
work. We
redetermine the structure from powder data using simulated
annealing
and show that the conformational disorder is clearly revealed
by this
method (C) 2003 Wiley-Liss, Inc.
TREOR
2003-38
Jorda, JL McCusker, LB Baerlocher, C
Morais, CM Rocha, J
Fernandez, C Borges, C Lourenco,
JP Ribeiro, MF Gabelica, Z
Structure analysis of the novel microporous aluminophosphate IST-1
using synchrotron powder diffraction data and HETCOR MAS
NMR
MICROPOROUS AND MESOPOROUS MATERIALS 65, 2003, 43-57.
A combination of advanced powder diffraction and NMR techniques have
allowed the structure of the novel microporous aluminophosphate
IST-1
(\(CH3NH2)(4)(CH3NH3+)(4)(OH-)(4)\[Al12P12O48] to be elucidated.
The
framework structure was determined in the non-centrosymmetric
space
group Pca2(1) (a = 9.61523(1) Angstrom, b = 8.67024(1)
Angstrom, c =
16.21957(2) Angstrom) from high-resolution synchrotron
powder
diffraction data using the program FOCUS. Extra framework
species were
then located on difference electron density maps. A hydroxyl
group was
found to bridge between two of the framework Al atoms,
and one
methylamine species, presumably protonated, could be located
in the
channels where it H-bonds to three framework oxygens.
The most unusual
feature of the structure is the second methylamine molecule,
which
bonds directly to a framework Al atom. The structure is
entirely
consistent with P-31 and Al-27 MAS NMR studies, which
showed there to
be three P (all 4-coordinate) and three At (one 4-, one
5- and one
6-coordinate) sites, and with C-13 MAS NMR, which showed
there to be
two different types of methylamine species in equal amounts.
Assignment
of the P-31, Al-27 and C-13 MAS NMR signals could be deduced
from the
crystallographic data, P-31-Al-27 HETCOR spectra and ab
initio
calculations.
N-TREOR
2003-39
Blomqvist, H Ronnebro, E Kyoi, D
Sakai, T Noreus, D
Structural characterization of Mg3MnH similar to 6 - a new
high-pressure phase synthesized in a multi-anvil cell
at 6 GPa
JOURNAL OF ALLOYS AND COMPOUNDS 358, 2003, 82-86.
With modem X-ray diffraction refinement methods it was shown to be
possible to identify a new Mg3MnH-6 phase from a minute
sample volume
in spite of poor crystallinity and coexisting impurity
phases. The new
hydride was synthesized at 6 GPa in a high-pressure multi-anvil
cell at
873 K. A monoclinic unit cell was found with a=8.827(2),
b=4.657(2),
c=4.676(2) Angstrom and beta=105.74(2)degrees, space group
P2(1)/m (no.
11), Z = 2, V = 184.99 Angstrom(3). Manganese is surrounded
by a
distorted cube of magnesium with average Mn-Mg distances
of 2.78(2)
Angstrom. The cubes share edges in the b and c directions
of the unit
cell but are separated by a distance of approximate to
3.6 Angstrom
along a, forming a layered structure. The hydrogen positions
were not
possible to determine, as only a small sample amount could
be prepared.
If the metal atom structure of the title compound is compared
to the
already known Mg3MnH7 it can be concluded that Mg3MnH-6
also consists
of manganese hydrido complexes counterbalanced by magnesium
ions, but
with a different alignment of the magnesium cubes.
N-TREOR
2003-40
Couhorn, U Dronskowski, R
Alkali-metal ortho-hydroxyphenolates: Syntheses and crystal structures
from powder X-ray diffraction
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 629, 2004, 2554-2558.
Colorless and highly air- and moisture-sensitive powders of
M[o-C6H4O(OH)] with M = K, Rb, or Cs have been synthesized
from
reaction mixtures of the appropriate alkali metal and
catechol in thf.
All compounds were structurally characterized by means
of powder X-ray
diffraction using the Rietveld profile refinement technique
including
restraints for the C-C/C-O bond distances and the C-C-C
angles. The
atomic arrangements of M[o-C6H4O(OH)] (K: monoclinic P2(1)/c;
Rb/Cs:
orthorhombic Pbcm) are characterized by polymeric chains
of
(1)(infinity)[M(1)([4])O(2)([2])eta(6)] units connected
by hydrogen
bonds, thereby making up layered structures similar to
the one of
catechol. The coordinatively unsaturated alkali metals
are forming
edge-sharing MO4 pyramids and exhibit asymmetrical eta(6)-interactions
with the phenylene rings. The symmetry of the unit cells
increases with
increasing size of the cation, and this results in a decrease
of the
monoclinic angle from 118.5degrees (catechol) to 93.7degrees
(K
compound), eventually leading to orthorhombic cells for
the Rb and Cs
compounds.
DICVOL
2003-41 ???
Guillou, N Livage, C Drillon, M
Ferey, G
The chirality, porosity, and ferromagnetism of a 3D nickel glutarate
with intersecting 20-membered ring channels
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 42, 2003, 5314-5317.
2003-42
Tedesco, E Della Sala, F Favaretto, L
Barbarella, G Albesa-Jove, D
Pisignano, D Gigli, G Cingolani,
R Harris, KDM
Solid-state supramolecular organization, established directly from
powder diffraction data, and photoluminescence efficiency
of rigid-core
oligothiophene-S,S-dioxides
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125, 2003, 12277-12283.
The "rigid-core" material
3,5-dimethyl-2,3'-bis(3-methylthiophene)-dithieno[3,2-b:',3'-d]thiophene
-4,4-dioxide (DTTOMe4) has the highest photoluminescence
ever reported
for thiophene-based molecules in the solid state. We report
the
structure of this material, determined directly from powder
X-ray
diffraction data using the Genetic Algorithm method for
structure
solution, followed by Rietveld refinement, and the structural
properties are discussed in relation to the structures
of the
corresponding subsystems DTTO and DTTOMe. While the crystal
structures
of the latter compounds contain cofacial dimers, the crystal
structure
of DTTOMe4 comprises layers of molecules aligned in an
antiparallel
fashion. Intermediate neglect of differential overlap
with single
configuration interaction (INDO/SCI) calculations on the
intermolecular
interactions in the three crystal structures show that
the different
solid-state photoluminescence efficiencies of DTTOMe4,
DTTOMe, and DTTO
cannot be correlated with the different types of dipole-dipole
alignment in the solid state. Instead, photoluminescence
efficiencies
correlate well with the rate of formation of nonradiatively
decaying
charge-transfer pairs upon photoexcitation. Because of
larger
intermolecular distances in DTTOMe4, the photoluminescence
is less
effectively quenched by charge-transfer processes than
in DTTOMe and
DTTO.
DICVOL
2003-43
Boudaren, C Auffredic, JP Louer, M
Louer, D
A powder X-ray diffraction study of lead chloride oxalate Pb2Cl2(C2O4):
ab initio structure determination and thermal behavior
POWDER DIFFRACTION 18, 2003, 205-213.
Mixed lead chloride oxalate, Pb2Cl2(C2O4), has been obtained in a
polycrystalline form in the course of a study on precursors
of
nanocrystalline PZT-type oxides. Its crystal structure
has been solved
ab initio from powder diffraction data collected using
a monochromatic
radiation from a conventional X-ray source. The symmetry
is monoclinic,
space group C2/m, the cell dimensions are a = 5.9411(3)
Angstrom, b =
5.8714(4) Angstrom, c = 9.4212(4) Angstrom, beta = 95.232(4)degrees
and
Z = 2. The structure consists of a stacking of complex
double sheets,
built from lead polyhedra, parallel to (001) and connected
together
through oxalate groups. The lead atom is nine-fold coordinated
by four
0 atoms from one bidentate and two monodentate oxalate
groups and five
Cl atoms. The polyhedron can be described as a highly
distorted square
antiprism mono-capped by a Cl atom. The thermal behavior
of lead
chloride oxalate, in vacuum and in air, is carefully described
from
temperature-dependent powder diffraction and thermogravimetric
measurements. It is shown that reaction pathways are complicated
by the
identification of various oxide chloride phases.
DICVOL
2003-44 ???
Barthelet, K Adil, K Millange, F
Serre, C Riou, D Ferey, G
Synthesis, structure determination and magnetic behaviour of the first
porous hybrid oxyfluorinated vanado(III)carboxylate: MIL-71
or
V-2(III)(OH)(2)F-2{O2C-C6H4-CO2} . H2O
JOURNAL OF MATERIALS CHEMISTRY 13, 2003, 2208-2212.
A new type of three-dimensional vanadium(III) dicarboxylate, MIL-71
or
V-2(III)(OH)(2)F-2{O2C-C6H4-CO2}.H2O, has been obtained
under
hydrothermal conditions from aqueous mixtures of vanadium,
1,4-benzenedicarboxylic acid, and HF. MIL-71cal or
(V2O2F2)-O-IV{O2C-C6H4-CO2} is obtained by calcination
of the parent
compound in air at 250 degreesC. The three-dimensional
structure of
MIL-71 (S.G.: Cmmm; a = 21.4477(8) Angstrom, b = 7.1449(2)
Angstrom, c
= 3.8246(2) Angstrom, and Z = 2) consists of layers built
from
corner-sharing {(VO2)-O-III(OH)(2)F-2} octahedra connected
by the
terephthalate linkers. The role of fluorine in this structure
is
understood by comparison with the already known hybrid
vanado(III)carboxylates. The thermal behavior of the two
solids has
been investigated using TGA and X-ray thermodiffractometry.
Finally,
magnetic measurements performed on both MIL-71 and MIL-71cal
reveal a
canted antiferromagnetic behavior with Neel temperatures
below 20 K.
DICVOL
2003-45
Corma, A Rey, F Valencia, S Jorda,
JL Rius, J
A zeolite with interconnected 8-, 10- and 12-ring pores and its unique
catalytic selectivity
NATURE MATERIALS 2, 2003, 493-497.
One of the major goals in catalysis is to improve the capabilities
of
microporous materials. This can be accomplished by synthesizing
new
zeolites; with controlled pore architectures. In particular,
zeolites
containing channels of different sizes in the same structure
are
desirable. Here, we report a zeolite containing fully
interconnected
8-, 10- and 12-membered-ring pores, synthesized by combining
the
structure-directing effect of the organic
1,5-bis-(methylpyrrolidinium)-pentane and the framework
isomorphic
substitution of germanium for silicon. Analysis of the
crystal
structure determined by direct methods from synchrotron
powder
diffraction data reveals 16 independent tetrahedrally
coordinated
atoms. This thermally and hydrothermally stable zeolite
structure, when
synthesized in its acidic form by incorporating aluminium
in the
framework, presents unique catalytic shape-selectivity
effects derived
from its particular pore topology.
DICVOL
2003-46
Stock, N Guillou, N Bein, T Ferey,
G
Inorganic-organic hybrid compounds: synthesis and crystal structure
determination from powder diffraction data of Sn-2[O3PCH2C6H4CH2PO3]
SOLID STATE SCIENCES 5, 2003, 629-634.
A new tin diphosphonate, Sn-2[O3PCH2C6H4CH2PO3], was hydrothermally
synthesized from alpha,alpha'-p-xylenediphosphonic acid
and SnC2O4. The
structure was solved and refined using X-ray powder diffraction
data.
It crystallizes in the triclinic space group P (1) over
bar, with a =
4.9659(3), b = 5.4916(3), c = 11.1730(6) Angstrom, alpha
= 87.841(3),
beta = 93.827(4), gamma = 90.652(3)degrees, V = 303.79(8)
Angstrom(3),
Z = 1, R-WP = 0.107, R-P = 0.081, R-B = 0.075, R-F = 0.056.
The
structure is built up from [SnO3] polyhedra, containing
a
stereochemically active lone pair of electrons. These
polyhedra are
connected to a ladder-like structure by phosphonate groups,
RPO32-, and
through the organic pact of the diphosphonic acid to a
layered
structure. Thermogravimetric and IR spectroscopic studies
are also
presented.
DICVOL
2003-47
Sanchez-Migallon, A de la Hoz, A Lopez, C
Claramunt, RM Infantes, L
Motherwell, S Shankland, K Nowell,
H Alkorta, I Elguero, J
The structure of N-1-hydroxylophine N-3-oxide
(=1-hydroxy-2,4,5-triphenyl-1H-imidazole 3-oxide) in the
solid state
HELVETICA CHIMICA ACTA 86, 2003, 1026-1039.
The crystal structure of 1-hydroxy-2,4,5-triphenyl-1H-imidazole 3-oxide
(1) has been determined from laboratory X-ray powder-diffraction
data.
The two independent molecules in the asymmetric unit form
chains via
O-H ... O hydrogen bonds related by a twofold screw axis.
One of the O
... O distances is extremely short (2.32(1) and 2.43(1)
Angstrom).
Solid-state NMR spectroscopy (CPMAS) combined with calculation
of
absolute shieldings (GIAO/B3LW/6-31G*) allowed us to determine
that the
compound behaves as if the O-H ... O hydrogen bond has
the proton in
the middle (single-well potential), resulting in the near
identity of
both N-15-NMR signals.
DICVOL
2003-48
Boudaren, C Bataille, T Auffredic, JP
Louer, D
Synthesis, structure determination from powder diffraction data and
thermal behaviour of titanium(IV) oxalate [Ti2O3(H2O)(2)](C2O4)center
dot H2O
SOLID STATE SCIENCES 5, 2003, 175-182.
A titanium(IV) oxalate, [Ti2O3(H2O)(2)](C2O4).H2O, has been synthesised
in a polycrystalline form in the course of the study of
precursors of
PZT type oxides. Its crystal structure has been solved
ab initio from
powder diffraction data collected with conventional monochromatic
X-rays. The symmetry is orthorhombic, space group Cmca,
with cell
dimensions a = 15.494(2) Angstrom, b = 10.491 (1) Angstrom,
c =
9.700(l) Angstrom and Z = 8. The structure consists of
inorganic
corrugated layers of corner-sharing TiO6 octahedra, which
form infinite
-Ti-O-Ti- connections, linked together by the oxalate
anions. The
titanium environment is discussed with regard to bond-valence
calculations. The thermal behaviour of this compound has
been studied
by temperature-dependent X-ray diffraction and thermal
analyses. In the
course of the dehydration process, the partially dehydrated
phase
[Ti2O3(H2O)(2)](C2O4) has been isolated and its structure
has been
solved from in situ X-ray powder diffraction data. Its
crystal
structure determination has shown that the framework of
the precursor
is preserved. The complete decomposition scheme into anatase
is also
described.
DICVOL
2003-49 ??
Takata, M Nishibori, E Sakata, M
Wang, CR Shinohara, H
Sc-2 dimer in IPR-violated C-66 fullerene: a covalent bonded
metallofullerene
CHEMICAL PHYSICS LETTERS 372, 2003, 512-518
The structure of an IPR-violated metallofullerene Sc-2@C-66 has been
determined in the electron density level by the MEM/Rietveld
method
using synchrotron radiation powder data. The fundamental
structure has
been obtained by the Rietveld analysis. The cage structure
of C-66 has
been unambiguously identified as that of Isomer No. 4348.
The obtained
charge density by the MEM analysis shows that the encapsulated
two Sc
atoms form the covalent bonded Sc-2 dimer and that the
charge density
of dimer is overlapping with that of C-66 cage, indicating
the
existence of a covalent bond character between Sc-2 and
the carbon
cage.
DICVOL
2003-50 ??
Cacela, C Baudot, A Duarte, ML Matos-Beja,
AM
Silva, MR Paixao, JA Fausto, R
Low temperature polymorphism in 3-amino-1-propanol
JOURNAL OF MOLECULAR STRUCTURE 649, 2003, 143-153.
3-Amino-1-propanol (3AP) was investigated by differential scanning
calorimetry, and low temperature powder X-ray diffraction
and Raman
spectroscopy. Within the range of temperatures studied
(-150-25
degreesC), 3AP was found to be able to crystallize in
two monotropic
polymorphs. Fast cooling rates produce an amorphous state
that, on
heating, crystallizes into the metastable polymorph. At
higher
temperatures, this metastable crystalline phase converts
into the
stable crystal. Using intermediate cooling rates, 3AP
crystallizes as
the metastable polymorph, the solid solid transition leading
to
conversion of this form into the stable polymorph occurring
during the
subsequent heating. Slower cooling rates enable formation
of the stable
crystal on cooling. The two crystalline polymorphs were
structurally
characterized by powder X-ray diffraction and Raman spectroscopy.
It
was concluded that different conformations are assumed
by the
individual molecules of 3AP in the two crystalline varieties,
with the
molecules assuming the all-trans configuration in the
metastable
crystalline state and having the heavy atom backbone trans
but the NH2
and OH groups gauche in the-stable crystal.
DICVOL
2003-51
Barthelet, K Riou, D Nogues, M Ferey,
G
Synthesis, structure, and magnetic properties of two new
vanadocarboxylates with three-dimensional hybrid frameworks
INORGANIC CHEMISTRY 42, 2003, 1739-1743.
(V-III(OH))(2){C6H2(CO2)(4)}.4H(2)O (labeled MIL-60) and
VIII(OH){(2)(O2C)C6H2(COOH)(2)}.H2O (labeled MIL-61) were
hydrothermally synthesized from mixtures of VCl3,
1,2,4,5-benzenetetracarboxylic acid, and water heated
for 3 days at 473
K The structure of MIL-60 was solved from single-crystal
X-ray
diffraction data in the triclinic centrosymmetric P1 (No.
2) space
group with lattice parameters a = 6.3758(5) Angstrom,
b = 6.8840(5)
Angstrom, c = 9.0254(5) Angstrom, alpha = 69.010(2)degrees,
beta =
85.197(2)degrees, gamma = 79.452(2)degrees, V = 363.53(5)
Angstrom(3),
and Z = 1. The structure of MIL-61 was ab initio determined
from an
X-ray powder diffraction pattern. MIL-61 crystallizes
in the Pnma (No.
62) orthorhombic space group with lattice parameters a
= 14.8860(1)
Angstrom, b = 6.9164(l) Angstrom, c =10.6669(2) Angstrom,
V =
1098.23(3) Angstrom(3), and Z = 4. Both structures contain
the same
inorganic building block that consists of trans chains
Of
(VO4)-O-III(OH)(2) octahedra. The three-dimensional frameworks
of
MIL-60 and MIL-61 are constituted by the linkage of these
chains via
the organic molecules so delimiting the channels or cages
where the
water molecules are encapsulated. The magnetic behavior
of these two
phases is presented: MIL-60 is paramagnetic, and MIL-61
antiferromagnetically orders below T-N = 55(5) K.
DICVOL
2003-52
Guillou, N Livage, C van Beek, W
Nogues, M Ferey, G
A layered nickel succinate with unprecedented hexanickel units:
Structure elucidation from powder-diffraction data, and
magnetic and
sorption properties
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 42, 2003, 644-647.
DICVOL
2003-53
Ma, HA Jia, X Cui, QL Pan, YW
Zhu, PW Liu, BB
Liu, HJ Wang, XC Liu, J
Zou, GT
Crystal structures of C3N6H6 under high pressure
CHEMICAL PHYSICS LETTERS 368, 2003, 668-672.
In situ high-pressure energy-dispersive X-ray diffraction (EDXRD)
experiments on melamine (C3N6H6) have been carried out
using diamond
anvil cell (DAC) with synchrotron radiation source. In
the pressure
range from ambient pressure up to 14.7 GPa, two pressure-induced
structure phase transitions, from monoclinic to triclinic
structure at
about 1.3 GPa and from triclinic to orthorhombic structure
at about 8.2
GPa, are observed. The crystal structures of melamine
at different
pressures are built by using Materials Studio (MS) based
on the
principle of energy minimization.
DICVOL
2003-54
Khan, MS Al-Mandhary, MRA Al-Suti, MK
Corcoran, TC Al-Mahrooqi, Y
Attfield, JP Feeder, N David,
WIF Shankland, K Friend, RH
Kohler, A Marseglia, EA Tedesco,
E Tang, CC Raithby, PR
Collings, JC Roscoe, KP Batsanov,
AS Stimson, LM Marder, TB
Synthesis and optical characterisation of platinum(II) poly-yne
polymers incorporating substituted 1,4-diethynylbenzene
derivatives and
an investigation of the intermolecular interactions in
the
diethynylbenzene molecular precursors
NEW JOURNAL OF CHEMISTRY 27, 2003, 140-149.
A series of 1,4-diethynylbenzene (1) derivatives, H-Cequivalent
toC-R-Cequivalent toC-H with R=C6H3NH2 (2), C6H3F(3),
C6H2F2-2,5 (4),
C6F4 (5), C6H2(OCH3)(2)-2,5 (6) and C6H2 ((OC8H17)-C-n)(2)-2,5
(7) has
been synthesised and their crystal structures determined
by single
crystal (2-5) or powder (6, 7) X-ray diffraction. The
Cequivalent
toCH...pi(Cequivalent toC) hydrogen bonds dominating structure
1 are
gradually replaced by Cequivalent toC-H...F ones with
the increase of
fluorination (3-->5), or completely replaced by Cequivalent
toCH...N
and NH...pi(Cequivalent toC) bonds in 2, and Cequivalent
toCH...O in 6
and 7. The related platinum-based polymers,
trans-[Pt((PBu3)-Bu-n)(2)-Cequivalent toC-R-Cequivalent
toC-](n) (R=as
above and C6H4,) have been prepared and characterised
by spectroscopic
methods and thermogravimetry, which show that the amino-
and
methoxy-derivatives have lowest thermal stability while
the fluorinated
ones exhibit increasing thermal stability with increasing
fluorination.
Optical spectroscopic measurements reveal that substituents
on the
aromatic spacer group do not create strong donor-acceptor
interactions
along the rigid backbone of the organometallic polymers.
DICVOL
2003-55
Nockemann, P Cremer, U Ruschewitz, U
Meyer, G
Mercurous azide, Hg-2(N-3)(2)
ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE 629, 2003, 2079-2082.
White polycrystalline mercurous azide, Hg-2(N-3)(2), is obtained by
combining aqueous solutions of NaN3 and Hg-2(NO3)(2).2H(2)O
(made
viscuous by addition of tetramethoxysilane and heating
at 65 degreesC).
The crystal structure was solved and refined from X-ray
powder
diffraction data (monoclinic, P2(1)/n, a = 596.07(2) pm,
b = 1259.07(4)
pm, c = 357.95(1) pm, beta 103.253(2)degrees, Z = 2, R-B
= 0.0519).
Solid Hg-2(N-3)(2) contains, essentially, molecules of
that composition
with Hg-Hg distances of 254.4(3) pm, Hg-N distances of
218(2) pm and
Hg-Hg-N angles of 178.7(6)degrees. Weak intermolecular
interactions
with Hg-N distances starting at 280(3) pm lead to a three-dimensional
structure.
2003-56
Nalini, G Subbanna, GN Row, TNG
Studies on n=2 Aurivillius phases: structure of the series
Bi3-xLaxTiNbO9 (0 <= x <= 1)
MATERIALS CHEMISTRY AND PHYSICS 82, 2003, 663-671.
The crystal structures of the solid solutions of Bi3-xLaxTiNbO9 (0
less
than or equal to x less than or equal to 1) have been
analyzed by
powder X-ray diffraction with supporting evidence from
selected area
electron diffraction (SAD). The structure of the starting
member (x =
0) is verified to be in the orthorhombic space group A2(1)
am while the
end member (x = 1) is determined to crystallize in the
centrosymmetric
orthorhombic space group Pmcb. The structure of x = 1
phase is solved
by ab initio powder diffraction. The intermediate compositions
belong
to the space group A2(1) am as confirmed by Rietveld refinements.
Rietveld refinements on all the compositions reveal that
the La3+ ion
is disordered only in the A site and not in the [Bi2O2](2+)
layer. The
tilt in the Ti/NbO6 octahedra decreases with increasing
x.
2003-57 ???
Ju, J Lin, JH Li, GB Yang, T
Li, HM Liao, FH Loong, CK You, LP
Aluminoborate-based molecular sieves with 18-octahedral-atom tunnels
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 42, 2003, 5607-5610
2003-58 ???
AU Yebra-Rodriguez, A Martin-Ramos, JD del Rey,
F Viseras, C Lopez-Galindo, A
Effect of acid treatment on the structure of sepiolite
CLAY MINERALS 38, 2003, 353-360.
An ab initio determination of the structure of sepiolite after acid
treatment (HCI 0.5 N for 24 h) was carried out using X-ray
powder
diffraction data. After acid treatment, the sections normal
to the a
and c axes presented discontinuities, similar to2.25 Angstrom
wide,
parallel to the (0 10) plane, with no electronic density
maxima, thus
suggesting that adjacent planes are joined by van der
Waals-like
residual links. Partial dissolution was detected oil both
octahedral
and tetrahedral sheets, beginning by breaking the ribbons
not along the
edges, but in the centre, thus creating a 5.20 x 6.79
Angstrom tunnel
along the a axis. By interrupting the tetrahedral sheet,
this mechanism
changes the phyllosilicate-like nature of the sepiolite
to an
inosilicate-like structure.
2003-59 ???
Plevert, J Sanchez-Smith, R Gentz, TM
Li, HL Groy, TL
Yaghi, OM O'Keeffe, M
Synthesis and characterization of zirconogermanates
INORGANIC CHEMISTRY 42, 2003, 5954-5959.
Six new zirconogermanates have been prepared under hydrothermal
conditions using amines as bases. There are four new structure
types
(ASU-n) with a common motif of ZrGe5. ASU-23 is a layered
structure:
ZrGe3O8(OH)F.[C10H26N4].H2O, space group P2(1)/n, a =
6.7957(8)
Angstrom, b = 12.700(1) Angstrom, c = 24.293(3) Angstrom,
beta =
97.936(2)degrees, V = 2076.4(4) Angstrom(3). ASU-24 is
a pillared
layered structure:
Zr3Ge6O18(OH2,F)(4)F-2.[C6H18N2](2).[C6H17N2](2).2H(2)O,
space group
P2(1)/n, a = 7.4249(3) Angstrom, b = 25.198(1) Angstrom,
c = 11.3483(5)
Angstrom, beta = 90.995(1)degrees, V = 2122.9(2) Angstrom(3).
This
material has the lowest framework density (FD) of any
oxide material
that we are aware of (FD = 8.48 metal atoms/nm(3)). Two
other materials
form three-dimensional open-frameworks, ASU-25: ZrGe3O9.[C3H12N2],
space group P112(1)/a, a = 13.1994(4) Angstrom, b = 7.6828(2)
Angstrom,
c = 11.2373(3) Angstrom, gamma = 91.233(3)degrees, V =
1139.29(5)
Angstrom(3). The other is ASU-26: ZrGe3O9.[C2H10N2], space
group Pn, a
= 13.7611(3) Angstrom, b = 7.7294(2) Angstrom, c = 11.2331(3)
Angstrom,
beta = 104.793(1)degrees, V = 1155.21(4) Angstrom(3).
ASU-25 is related
to the mineral umbite K2ZrSi3O9.H2O. The germanium equivalent
has been
prepared through the inorganic route: K2ZrGe3O9.H2O, space
group
P2(1)2(1)2(1), a = 13.6432(6) Angstrom, b = 7.4256(3)
Angstrom, c =
10.3973(4) Angstrom, V = 1053.33(8) Angstrom(3). The structural
relationships between ASU-25 and its inorganic counterpart
are
described. The thermal decomposition of the germanium
umbite generated
the cyclic trigermanate K2ZrGe3O9, analogue of the mineral
wadeite,
crystallizing in the orthorhombic system, a = 7.076 Angstrom,
b =
12.123 Angstrom, c = 10.451 Angstrom, V = 904.5 Angstrom(3).
2003-60
Crossland, CJ Evans, JSO
Synthesis and characterisation of a new high pressure polymorph of
Cu2WS4
CHEMICAL COMMUNICATIONS iss 18, 2003, 2292-2293.
In this communication we report the synthesis and structural
characterisation of a new body centred polymorph of Cu2WS4
prepared
using hydrothermal methods. I-Cu2WS4 crystallises in space
group I (4)
over bar 2m with cell parameters a = b = 5.44427(8), c
= 10.0687(2)
Angstrom and has a new structure type containing layers
of edge-sharing
CuS4 and WS4 tetrahedra.
2003-61
Migdal-Mikuli, A Mikuli, E Hetmanczyk, L
Natkaniec, I
Holderna-Natkaniec, K Lasocha, W
Phase transitions, structural changes and molecular motions in
[Zn(NH3)(4)](BF4)(2) studied by neutron scattering, X-ray
powder
diffraction and nuclear magnetic resonance
JOURNAL OF SOLID STATE CHEMISTRY 174, 2003, 357-464.
Nuclear magnetic resonance (H-1 NMR and F-19 NMR) measurements
performed at 90-295K, inelastic incoherent neutron scattering
(IINS)
spectra and neutron powder diffraction (NPD) patterns
registered at
22-190 K, and X-ray powder diffraction (XRPD) measurements
performed at
86-293 K, provided evidence that the crystal of [Zn(NH3)(4)](BF4)(2)
has four solid phases. The phase transitions occurring
at: T-C3 = 101
K, T-C2 = 117 K and T-C1 = 178 K, as were detected earlier
by
differential scanning calorimetry (DSC), were connected
on one hand
only with an insignificant change in the crystal structure
and on the
other hand with a drastic change in the speed of the anisotropic,
uniaxial reorientational motions of the NH3 ligands and
BF4- anions (at
T-C3 and at T-C2) and with the dynamical orientational
order-disorder
process ("tumbling") of tetrahedral [Zn(NH3)(4)](2+) and
BF4- ions (at
T-C1). The crystal structure of [Zn(NH3)(4)](BF4)(2) at
room
temperature was determined by XRPD as orthorhombic, space
group Pnma
(No. 62), a = 10.523 Angstrom, b 7.892 Angstrom, c = 13.354
Angstrom
and Z = 4. Unfortunately, it was not possible to determine
the
structure of the intermediate and the low-temperature
phase. However,
we registered the change of the lattice parameters and
unit cell volume
as a function of temperature and we can observe only a
small deviation
from near linear dependence of these parameters upon temperature
in the
vicinity of the T-C1 phase transition.
2003-62
Kiang, YH Huq, A Stephens, PW Xu,
W
Structure determination of enalapril maleate Form II from
high-resolution X-ray powder diffraction data
JOURNAL OF PHARMACEUTICAL SCIENCES 92, 2003, 1844-1853.
The crystal structure of polymorphic Form II of enalapril maleate,
a
potent angiotensin-converting enzyme inhibitor, was determined
from
high-resolution X-ray diffraction data using the direct
space method.
Enalapril maleate Form II crystallizes in space group
P2(1)2(1)2(1), Z
= 4, with unit cell parameters a = 33.9898(3) Angstrom,
b = 11.2109(1)
Angstrom, c = 6.64195(7) Angstrom, and V = 2530.96(5)
Angstrom(3). By
treating the molecules as rigid bodies and using the bond
lengths and
angles obtained from the X-ray single crystal structures
of Form I,
which were solved almost 20 years ago, the total degrees
of freedom of
enalapril maleate were reduced from 25 to 12. This reduction
in total
degrees of freedom allowed the simulated annealing to
complete within a
reasonable computation time. In the crystal structure
of Form II, the
crystal packing, hydrogen-bonding pattern, and conformation
of
enalapril maleate resemble those in the structure of Form
I. The
crystal packing and conformation of enalapril maleate
in the two
polymorphic forms may explain the similarity of the thermal
properties,
C-13 nuclear magnetic resonance, Fourier transform infrared,
and Raman
spectra of Forms I and II. In both structures, the conformations
of the
main peptide chains, which are considered responsible
for binding the
active angiotensin-converting enzyme sites, remain largely
unchanged.
Lattice energy calculation showed that Form 11 is slightly
more stable
than Form I by 3.5 kcal/mole.
2003-63
Evans, IR Howard, JAK Evans, JSO
alpha-Bi2Sn2O7 - a 176 atom crystal structure from powder diffraction
data
JOURNAL OF MATERIALS CHEMISTRY 13, 2003, 2098-2103.
Pyrochlore-type bismuth tin oxide, Bi2Sn2O7, is a technologically
important material used in applications such as catalysis
and gas
sensing. Its room temperature structure has been solved
by a method of
simulated annealing of combined X-ray and neutron diffraction
data,
followed by Rietveld refinement. With 176 crystallographically
independent atoms in the asymmetric unit, it is one of
the largest
structures solved to-date from powder diffraction data.
In addition to
the number of unique atoms, additional crystallographic
difficulty
stems from the fact that the true symmetry of this structure
is lower
than the apparent metric symmetry of the unit cell.
2003-64
Irran, E Bein, T Stock, N
Inorganic-organic hybrid materials: synthesis and crystal structure
determination from powder diffraction data of Pb-2(O3PCH2C6H4CH2PO3)
JOURNAL OF SOLID STATE CHEMISTRY 173, 2003, 293-298.
A new lead diphosphonate, Pb-2(O3PCH2C6H4CH2PO3) was hydrothermally
synthesized from tetraethyl alpha,alpha'-p-xylenediphosphonate
and
Pb(NO3)(2). The structure was solved and refined using
X-ray powder
diffraction data. It crystallizes in the monoclinic space
group
P2(1)/c, with a = 467.84(2), b = 2007.98(9), c = 639.10(2)
pm, beta =
101.020(3)degrees, V = 589.31(4) 10(6) pm, Z = 2 wR(p)
= 0.034, R-p =
0.0277 R(F)2 = 0.061, R-F = 0.036. The structure is built
from
corner-linked [PbO4] polyhedra, containing a lone pair
of electrons.
These polyhedra are connected to layers by phosphonate
groups, RPO32-
and through the organic diphosphonic acid to a three-dimensional
structure. Thermogravimetric as well as IR spectroscopic
studies are
also presented.
2003-65
Paul-Boncour, V Filipek, SM Marchuk, I
Andre, G
Bouree, F Wiesinger, G Percheron-Guegan,
A
Structural and magnetic properties of ErFe2D5 studied by neutron
diffraction and Mossbauer spectroscopy
JOURNAL OF PHYSICS-CONDENSED MATTER 15, 2003, 4349-4359.
A neutron powder diffraction study of ErFe2D5, synthesized under 1
GPa
hydrogen pressure, shows that it crystallizes at room
temperature in an
orthorhombic structure described by the Pmn2(1) space
group with a =
5.42 Angstrom, b = 5.79 Angstrom, c = 8.00 Angstrom. The
deuterium
atoms order preferentially in some A(2)B(2) and AB(3)
interstitial
sites. Below 5 K the erbium moments order in a canted
magnetic
structure, with an erbium moment of 6.6 mu(B) at 1.4 K.
The Fe-57
Mossbauer spectra of ErFe2D5 from 4.2 to 300 K indicate
that there are
no ordered Fe moments at zero field. These results are
discussed in
relation to the influence of hydrogen absorption on the
magnetic
interactions.
2003-66
Dinnebier, RE Carlson, S Hanfland, M
Jansen, M
Bulk moduli and high-pressure crystal structures of minium, Pb3O4,
determined by X-ray powder diffraction
AMERICAN MINERALOGIST 88, 2003, 996-1002.
We report the pressure dependence of the crystal structure of lead
tetroxide (P less than or equal to 41.05 GPa, T 298 K)
using
high-resolution angle-dispersive X-ray powder diffraction.
Pb3O4 shows
two reversible phase transitions in the measured pressure
range. The
crystal structures of the modifications identified have
in common
frameworks of Pb+4O6 octahedra and irregular Pb+2O4+1
respectively
Pb2+O6+1 polyhedra. At ambient conditions, Pb3O4 crystallizes
in space
group P4(2)/mbc (phase 1). Between 0.11 and 0.3 GPa it
exhibits a
displacive second order phase transition to a structure
with space
group Pbam (phase II). A second displacive phase transition
occurs
between 5.54 and 6.6 GPa to another structure with space
group Pbam
(phase 111) but halved c dimension. A non-linear compression
behavior
over the entire pressure range is observed, which can
be described by
two Vinet relations in the ranges from 0.28 to 5.54 GPa
and from 6.6 to
41.05 GPa. The extrapolated bulk moduli of the high-pressure
phases
were determined to be K-0 = 21(2) GPa for phase 11 and
K-0 = 91(3) GPa
for phase III. The crystal structures of all phases were
refined from
X-ray diffraction powder data collected at several pressures
between
0.06 and 41.05 GPa. Except for their cell dimensions,
phases I and 11
were found to be isostructural to the corresponding phases
at low
temperatures, whereas phase III can be derived from the
Sr2PbO4
aristotype. With increasing pressure, the lone pair which
is localized
at Pb2+ adopts increasingly pure s-character, which is
reflected by the
similar coordination polyhedra of Ph2+ in Pb3O4 (phase
111) and of Sr2+
in Sr2PbO4.
2003-67 ????
Habereder, T Noth, H
Chemistry of boron, part 250 - 2-Triorgano-silyl, -germyl, -stannyl
and
-plumbyl derivatives of 1,3-diisopropyl-benzo-1,3,2-diazaborolidine
and
related compounds and their reactions with (eta(2)-C2H4)Pt(PPh3)(2)
APPLIED ORGANOMETALLIC CHEMISTRY 17, 2003, 525-538.
A series of 1,3-diisopropyl-benzo-1,3,2-diazaborolidines 1-6 carrying
ER3 substituents of Group 14 at the boron atom (E = C,
Si, Ge, Sn, Pb;
R = Me, Ph) have been prepared. Their molecular structures
have been
determined. As expected, the B-E bond length increases
along this
series. Moreover, the orientation of the isopropyl groups
relative to
the ER3 substituent is influenced by the steric demand
of these
substituents. The B-11 NMR data show a deshielding of
the boron nucleus
as the atomic weight of E increases. Oxidative addition
reactions with
(eta(2)-C2H4)Pt(PPh3)(2) were successful only for the
bromo derivative
I and the trimethylstannyl derivative 5a, they failed
for the
triphenylsilyl, triphenylgermyl. and triphenylstannyl
compounds,
indicating that steric effects play an important role
in the successful
oxidative addition to boryl-substituted
bis(triphenylphosphane)platinum(II) complexes. The triphenylplumbyl
derivative 6 reacted with (eta(2)-C2H4)Pt(PPh3)(2) to
give cis- and
trans-diphenyl-bis(triphenylphosphane)platinum besides
Ph(Ph3Pb)Pt(PPh3)(2). Obviously, the Pb-C bond is more
reactive than
the Pb-B bond. Cis-Platinum-boryl complexes were also
obtained from
(Me2N)(2)B-SnMe3 and (Me2N)(2)B-GeMe3 while the boranes
tmpB(SnMe3)(2)
and (Pr2NB)-Pr-i(SnMe3)(2) were unreactive.
2003-68
Li, LY Jin, XL Li, GB Wang, YX
Liao, FH Yao, GQ Lin, JH
Novel rare earth polyborates. 2. Syntheses and structures
CHEMISTRY OF MATERIALS 15, 2003, 2253-2260.
Three novel hydrated rare earth polyborates, Ln[B8O11(OH)(5)] (Ln =
La-Nd) (1), Ln[B9O13-(OH)(4)].H2O (Ln = Pr - Eu) (2),
and
Ce[B5O8(OH)]NO3.3H(2)O (3) have been synthesized by using
boric acid as
a flux at 240 degreesC, starting from rare earth oxides
or nitrates and
an excess of boric acid. All these polyborates crystallize
in
monoclinic structures (P2(1)/n) and consist of borate
sheets as the
fundamental unit, that is, [LnB(6)O(11)] sheet in 1 and
2 and [CeB5O9]
sheet in 3. The borate sheets all contain a nine-membered
borate ring,
of which the rare earth cations are located around the
center. The
borate frameworks in 1 and 3 are two-dimensional, which
are interlinked
via ionic Ln-O bonds forming 3D structures. While in 2
the borate
framework is three-dimensional with small channels filled
by water
molecules. Annealing the hydrated polyborates I and 2
at moderate
temperature leads to two anhydrous pentaborates, alpha-LnB(5)O(9)
(4)
for Ln = Pr-Eu and beta-LnB(5)O(9) (5) for Ln = La, Ce.
The structure
of beta-LaB5O9 has been determined by an ab initio method
using powder
X-ray diffraction data. It crystallizes in a monoclinic
structure in
the space group P2(1)/c with a = 6.4418(l) Angstrom, b
= 11.6888(3)
Angstrom, c = 8.1706(2) Angstrom, and beta = 105.167(1)degrees.
The
structure of beta-LnB(5)O(9) contains buckled nine-membered
ring borate
sheets that are interlinked by BO3 groups forming a three-dimensional
framework. The Eu3+-doped beta-LaB5O9 materials show dominant
D-5(0
-->) F-7(2) emission and a low quenching concentration
(0.6 at. %).
2003-69
Park, H Barbier, J Hammond, RP
Crystal structure and polymorphism of PbAlBO4
SOLID STATE SCIENCES 5, 2003, 565-571.
Two polymorphs of the new borate compound, PbAlBO4, have been
synthesized in microcrystalline form and their crystal
structures have
been refined from powder neutron diffraction data. The
low-temperature
form, alpha-PbAlBO4, crystallizes in the Pnma space group
with a =
6.9209(5) Angstrom, b = 5.7134(4) Angstrom, c = 8.0215(6)
Angstrom, Z =
4. Its structure is built of straight [010] chains of
edge-shared AlO6
octahedra bridged by BO3 groups and Pb2+ cations. The
high-temperature
form, beta-PbAlBO4, is obtained by heating the a form
to 1048 K
followed by quenching in air. It crystallizes in the Pbcn
space group
with a = 7.0423(3) Angstrom, b = 9.8989(3) Angstrom, c
= 9.4281(3)
Angstrom, Z = 8. The structure of beta-PbAlBO4 contains
zig-zag chains
of AlO6 octahedra bridged by BO3 groups and Pb2+ cations
and is related
to the structure of alpha-PbAlBO4 by unit-cell twinning.
The detailed
crystal chemical analysis of the alpha- and beta-PbAlBO4
structures
shows that the alpha-->beta transformation is driven by
a decrease in
density and the relief of bonding and non-bonding, interactions
around
the Pb2+ cations.
2003-70
Brunelli, M Wright, JP Vaughan, GRM
Mora, AJ Fitch, AN
Solving larger molecular crystal structures from powder diffraction
data by exploiting anisotropic thermal expansion
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 42, 2003, 2029-2032.
2003-71
Brinks, HW Hauback, BC
The structure of Li3AlD6
JOURNAL OF ALLOYS AND COMPOUNDS 354, 2003, 143-147.
The structure of Li3AlD6 has been determined by combined synchrotron
X-ray and neutron diffraction. The space group is R3 with
unit-cell
dimensions a = 8.07117(10) and c = 9.5130(2) Angstrom.
The structure
consists of isolated and close to regular AlD63- octahedra,
which are
connected via six-coordinated Li. The Al-D distances are
1.734-1.754
Angstrom, and the Li-D distances are 1.892-2.120 Angstrom.
The shortest
D-D distance of 2.395 Angstrom is found within the octahedra.
The
structure can be described as a distorted bcc structure
of AlD63- units
with all tetrahedral sites filled with Li.
2003-72
AU Kongshaug, KO Fjellvag, H
Novel coordination polymers based on nickel(II) and
2,6-naphthalenedicarboxylate
SOLID STATE SCIENCES 5, 2003, 303-310.
The two coordination polymers [Ni(ndc)(lutidine)(2)(H2O)(2)], CPO-3,
and [Ni-3(ndc)(3)(pyridine)(4)], CPO-4, were obtained
by hydrothermal
reactions between 2,6-naphthalenedicarboxylic acid (ndc),
3,4-lutidine
and nickel(II) nitrate (CPO-3) and ndc, pyridine and nickel(II)
nitrate
(CPO-4), respectively. In CPO-3, the combination of octahedral
nickel(II) ions and ndc ligands leads to the formation
of infinite
chains. CPO-4 is based on linear trinuclear building units
of
octahedral nickel(II) ions that are crosslinked via the
ndc ligands to
form a 3D-structure. The crystal structure of CPO-3 was
solved from
synchrotron powder X-ray data, while the crystal structure
of CPO-4 was
solved from conventional single-crystal X-ray data. Crystal
data for
CPO-3: monoclinic space group Cc (No. 9), a = 14.8583(2),
b =
20.3985(3), c = 10.7258(1) Angstrom, beta = 129.0067(6)degrees,
V =
2526.14(5) Angstrom(3) and Z = 4. Crystal data for CPO-4:
monoclinic
space group P2(1)/c (No. 14), a = 11.491(3), b = 17.917(4),
c =
12.781(3) Angstrom, beta = 116.142(7)degrees, V = 2362.2(9)
Angstrom(3)
and Z = 2. The thermal and magnetic properties of both
compounds were
investigated.
2003-73
Renaudin, G Bertheville, B Yvon, K
Synthesis and structure of an orthorhombic low-pressure polymorph of
caesium magnesium hydride, CsMgH3
JOURNAL OF ALLOYS AND COMPOUNDS 353, 2003, 175-179.
CsMgH3 was synthesized by heating mixtures of the binary hydrides in
an
autoclave at 600 K and a hydrogen pressure of 150 bars.
Synchrotron
X-ray and neutron powder diffraction reveals a new structure
having
orthorhombic symmetry (space group Pmmn, a = 9.9958(1),
b = 6.13271(6),
c = 8.57364(9) Angstrom for the hydride). In contrast
to the trigonal
high-pressure polymorph, magnesium centred [MgH6] octahedrons
are
condensed into triangular rather than linear [3MgH(3)](3-)
trimers, and
these trimers are connected via four corners to two-dimensional
slabs
rather than via six corners to a three-dimensional network.
The Mg-D
distances in the deuteride range from 1.94 to 1.96 Angstrom
at the
periphery to 2.00-2.08 Angstrom at the centre of the trimers.
The Mg
displacements within the octahedrons suggest repulsive
Mg2+-Mg2+
interactions.
2003-74
Harvey, HG Teat, SJ Tang, CC Cranswick,
LM Attfield, MP
Synthesis and characterization of three novel cation-containing
(NH4+/(CHNH3+)-H-3-N-7/NH3+C2H4NH3+) aluminum diphosphonates
INORGANIC CHEMISTRY 42, 2003, 2428-2439.
Three new aluminum diphosphonates (C3H7NH3){AIF[(HO)O2PC2H4PO3]} (1)
(orthorhombic, Pnma, a = 8.2048(l) Angstrom, b = 6.90056(6)
Angstrom, c
= 19.6598(4) Angstrom, Z = 4), (H3NC2H4NH3)[AI(OH)(O3PC2H4PO3)]
(2)
(monoclinic, P2(1)/n, a = 11.142(3) Angstrom, b = 7.008(2)
Angstrom, c
= 12.903(5) Angstrom, = 96,24(7)degrees, Z = 4), and
(NH4)2[AIF(O3PCH2PO3)](3) (orthorhombic, Cmcm, a = 16.592(2)
Angstrom,
b = 7.5106(g) Angstrom, c = 7.0021 (9) Angstrom, Z = 4)
have been
synthesized by solvothermal methods in the presence of
linear organic
ammonium cations (for 1 and 2) and ammonium cations (for
3) and their
structures determined using powder, microcrystal, and
single-crystal
X-ray diffraction data, respectively. All three materials
contain a
similar one-dimensional chain motif which is related to
that found in
the mineral Tancoite. This chain motif consists of corner-sharing
octahedra (AIO(4)F(2) for 1 and 3 and AIO(6) for 2) linked
together
through the bridging CPO3 tetrahedra of the diphosphonate
groups. These
chains are unusual in that each diphosphonate moiety acts
as a
bisbidentate ligand that is coordinated to the same two
metal centers
through both of the O3PC-groups of the diphosphonate ligand.
The
arrangement of the Tancoite-like chains and charge compensation
cations
in the structures of compounds 1-3 is seen to be dependent
upon the
nature of the diphosphonic acid and organoammonium/ammonium
cations.
Careful selection of these two components may provide
a method to
design future materials in this system.
2003-75 ?????
Jeong, HK Nair, S Vogt, T Dickinson,
LC Tsapatsis, M
A highly crystalline layered silicate with three-dimensionally
microporous layers
NATURE MATERIALS 2, 2003, 53-58.
Layered silicates with three-dimensional microporosity within the
layers have the potential to enable new applications in
catalysis,
adsorption and ion-exchange. Until now no such materials
have been
reported. However, here we present the synthesis and structure
of
AMH-3, a silicate with three-dimensionally microporous
layers, obtained
in high purity and crystallinity. AMH-3 is composed of
silicate layers
containing eight-membered rings in all three principal
crystal
directions, and spaced by strontium cations, sodium cations
and water
molecules. Because of its three-dimensional pore structure,
acid and
thermal stability, this layered material could find applications
in
polymer-silicate composites for membrane applications,
for synthesis of
combined microporous-mesoporous materials, and for the
formation of new
zeolites and microporous films. Its existence also opens
new
possibilities for the synthesis of other layered silicates
with
multidimensional microporous framework layers.
AMH-3, Na8 Sr8 Si32 O76 .16 H2 O, C2/c, conventtional X-ray + synchrotron
data,
No program name given for indexation, EXPO for "|Fobs|" extraction
(Le Bail
method), EXPO for direct methods, locating all one Sr and four Si atoms
(5 of a
total of 19 independent atoms), completion by alternating Rietveld
and Fourier
difference using GSAS on the synchrotron data
2003-76
Plevert, J Gentz, TM Groy, TL O'Keeffe,
M Yaghi, OM
Layered structures constructed from new linkages of Ge-7(O,OH,F)(19)
clusters
CHEMISTRY OF MATERIALS 15, 2003, 714-718.
Three new germanate solids, ASU-19, ASU-20-DAPe, and ASU-20-DACH, have
been synthesized under hydrothermal conditions using respectively
1,4-diaminobutane (DAB), 1,5-diaminopentane (DAPe), and
1,4-diaminocyclohexane (DACH) as bases. The structures
of ASU-19 and
ASU-20-DACH have been characterized by single-crystal
X-ray
diffraction: ASU-19, Ge14O29X4.[GeOX2].[H(2)DAB](3).3.8H(2)O
(X = F or
OH), space group P (1) over bar, a = 11.4191(5), b = 12.05250,
c =
18.1847(8) Angstrom, alpha = 90.704(1)degrees, beta =
92.635(1)degrees,
gamma = 91.389(1)degrees, V = 2499.1(2) Angstrom(3); ASU-20-DACH:
Ge7O14X3.[H(2)DACH](1.5).2H(2)O, space group C2/c, a =
15.9525(11), b =
17.5476(12), c = 19.0027(13) Angstrom, beta = 109.446(1)degrees,
and V
= 5015.90 Angstrom(3). The structure of ASU-20-DAPe,
Ge7O14X3.[H(2)DAPe](1.5).H2O, has been determined from
X-ray powder
diffraction data: space group C2/c, a = 16.3180(5), b
= 16.6125(4), c =
17.8898(6) Angstrom, beta = 99.684(2)degrees, V = 4780.5(3)
Angstrom(3). All three structures are based on the assembly
of the same
cluster Ge-7(O,OH,F)(19). The two ASU-20 structures consist
of a slab
of four-connected clusters. In ASU-19, the same layers
are connected
pairwise through a GeO2X2 spacer, generating a slab structure,
with
slab thickness ca. 20 Angstrom. The existence of the same
layer in the
presence of three different organic bases shows the adaptability
of the
structures to molecules differing in size, shape, and
symmetry.
2003-77
Bie, LJ Wang, YX Lin, JH Loong,
CK Richardson, JW
You, LP Dong, C
Synthesis and structure of n=5 member of the A(n+1)Mn(n)O(3n+3)(A(2)O)
series
CHEMISTRY OF MATERIALS 15, 2003, 516-522.
La4Ba2.6Ca1.4(Mn4Ca)O-19, a novel hexagonal perovskite-intergrowth
manganate, was synthesized by solid-state reaction. It
crystallizes in
the space group C2/m (no. 12) with the lattice parameters
of a =
9.8394(4) Angstrom, b = 5.6823(2) Angstrom, c = 15.6435(3)
Angstrom,
and beta = 102.093(5), cell volume of 855.21(5) Angstrom(3),
and Z = 2.
The structure was investigated by electron, X-ray, and
neutron
diffraction techniques and fully resolved by refinements
of both X-ray
and neutron powder diffraction data. The structure can
be described as
alternate stacking of 6H-type hexagonal perovskite blocks
and
graphite-like Ca2O sheets. In the hexagonal perovskite
block, Mn and Ca
cations occupy the octahedral sites of the corner-shearing
and
face-shearing octahedra, respectively. Preferred La/Ba
and Ca/La
substitution at the ratio of 7:3 was observed over specific
crystallographic sites. La(4)Ba(2.6)Cal(1.4)(Mn4Ca)O-19
is an n = 5
member of the A(n+1)Mn(n)O(3n+3)(Ca2O) series in which
1/5 of the Mn
atoms in the 6H-hexagonal perovskite blocks are replaced
by Ca. A
structural principle that is based on alternate stacking
of
close-packed [AO(3)] layers and graphite-like sheets is
introduced for
structural prediction of new hexagonal perovskite intergrowth
compounds.
2003-78
Dinnebier, RE Vensky, S Jansen, M
Crystal and molecular structure of rubidium peroxodicarbonate Rb-2[C2O6]
CHEMISTRY-A EUROPEAN JOURNAL 9, 2003, 4391-4395.
We report the crystal structure of rubidium peroxodicarbonate, which
was synthesized by electrocrystallization at T = 257 K,
from laboratory
X-ray powder diffraction data. The compound crystallizes
in the
monoclinic space group P2(1)/c with four formula units
per unit cell
and cell parameters of a=7.9129(1), b=10.5117(1), c=7.5559(1)
Angstrom,
beta=102.001(1)degrees, and V=614.75(1) Angstrom(3). The
packing can be
considered as a strongly distorted CsCl type of structure.
The
conformation of the peroxodicarbonate anion was found
to be planar
(C-2h symmetry), in contrast to the staggered conformation
of the
peroxodicarbonate anion in the respective potassium peroxodicarbonate.
ne different conformation is attributed to packing effects.
2003-79
Botez, CE Stephens, PW Nunes, C
Suryanarayanan, R
Crystal structure of anhydrous delta-D-mannitol
POWDER DIFFRACTION 18, 2003, 214-218.
The crystal structure of anhydrous delta-D-mannitol (C6H14O6) was
solved from high-resolution synchrotron X-ray powder diffraction
data
collected on a mixture containing 20% and 80% w/w of beta-
and
delta-D-mannitol, respectively. The direct space simulated
annealing
program PSSP, and Rietveld analysis employing GSAS were
used to
determine and refine the structure. The polymorph has
monoclinic
symmetry, space group P2(1) with a = 5.089 41(5) Angstrom,
b =
18.2504(2) Angstrom, c = 4.917 02(5) Angstrom, and beta
=
118.303(2)degrees. There is one molecule in the irreducible
volume of
the unit cell. The pattern of hydrogen bonding is significantly
different than the previously known a and 8 forms.
2003-80
Friese, K Honnerscheid, A Jansen, M
Crystal structure determination of systematically intergrown compounds:
Li-5(OH)(2)Br-3 and Li-2(OH)Br
ZEITSCHRIFT FUR KRISTALLOGRAPHIE 218, 2003, 536-541.
We carried out a structure refinement of a crystal which was composed
of two phases. Phase I was up to now unknown and corresponds
to
Li-5(OH)(2)Br-3 with lattice parameters a = 4.02335(1),
c = 21.5638(1)
Angstrom, space group Mm2. Phase H is Li-2(OH)Br with
lattice
parameters a = 4.04594(3) Angstrom and space group Pm3m.
The two phases
have the a, b-plane in common and consequently part of
the reflections
overlap systematically. We performed a joint structure
refinement of
the two phases taking into account all reflections. The
structure of
Li-5(OH)(2)Br-3 is characterized by anti-perovskite like
double layers
of composition 2 x Li-2(OH)Br, which alternate with rock-salt
like
layers of composition LiBr. Results for Li-2(OH)Br are
in good
agreement with literature and confirm the correctness
of the underlying
model and the usefulness of the method employed in structure
refinement.We carried out a structure refinement of a
crystal which was
composed of two phases. Phase I was up to now unknown
and corresponds
to Li-5(OH)(2)Br-3 with lattice parameters a = 4.02335(1),
c =
21.5638(1) Angstrom, space group I (4) over bar m2. Phase
II is
Li-2(OH)Br with lattice parameters a = 4.04594(3) Angstrom
and space
group Pm (3) over barm. The two phases have the a, b-plane
in common
and consequently part of the reflections overlap systematically.
We
performed a joint structure refinement of the two phases
taking into
account all reflections.
The structure of Li-5(OH)(2)Br-3 is characterized by anti-perovskite
like double layers of composition 2 x Li-2(OH)Br, which
alternate with
rock-salt like layers of composition LiBr. Results for
Li-2(OH)Br are
in good agreement with literature and confirm the correctness
of the
underlying model and the usefulness of the method employed
in structure
refinement.
2003-81
Bauer, EM Bellitto, C Ibrahim, SA
Mahmoud, MR Righini, G
Ni(II)octadecylphosphonate: an inorganic/organic layered
weak-ferromagnet
POLYHEDRON 22, 2003, 2463-2469.
Ni[CH3(CH2)(17)PO3] . H2O was prepared and characterized by several
techniques and the magnetic properties were measured by
using a SQUID
magnetometer. Preliminary refinement of the X-ray diffraction
powder
data by structure-less Le Bail fitting could be obtained
and the
compound was found to crystallise in the orthorhombic
space group
Pmn2(1) with a = 5.478(7) Angstrom, b = 42.31(4) Angstrom,
c = 4.725(3)
Angstrom. Ni(II)octadecyl phosphonate is lamellar and
the structure
consists of alternating inorganic and organic layers.
The inorganic
layers are interspersed by by-layers of the octadecyl
substituent and
van der Waals contacts are established between them. IR
spectroscopy
revealed all-trans configuration of the hydrocarbonic
chain. A tilt
angle of 48.2degrees between the chain axis and the (ac)
plane could be
estimated. The temperature dependence of the molar susceptibility
plotted as 1/chi vs. T is linear above 100 K and it follows
the
Curie-Weiss law. The Curie, C, constant suggests the presence
of Ni(II)
ion in the S = I spin state and the negative Weiss, theta,
constant is
indicative of antiferromagnetic nearest neighbour exchange
interactions. Zero-field and field-cooled chi vs. T plots
were then
recorded. The plots show no overlap below 20 K, thus indicating
that
the compound is in an ordered magnetic state. The critical
temperature
has been located at the onset of the X vs. T plot and
was found to be
T-N = 21 K. The magnetization vs. field plots, measured
at different
temperatures, provide the indication that the compound
is a
weak-ferromagnet below TN.
2003-82
Howard, CJ Zhang, ZM
Structures and phase transition in the layered perovskite
La0.6Sr0.1TiO3: a new orthorhombic structure solved from
high-resolution diffraction in combination with group
theoretical
analysis
JOURNAL OF PHYSICS-CONDENSED MATTER 15, 2003, 4543-4553.
The crystal structure of the layered perovskite La0.6Sr0.1TiO3 at room
temperature has been solved by synchrotron x-ray powder
diffraction in
combination with group theoretical analysis. The structure
is
orthorhombic in Cmmm, on a cell with a = 7.7556(l), b
= 7.7349(l) and c
= 7.7910(l) Angstrom. It is believed that this is also
the structure
adopted by La2/3TiO3. Pertinent features are the alternation
of fully
and partly occupied layers of La (Sr) cations, and out-of-phase
tilting
of the TiO6 octahedra around an axis perpendicular to
the direction of
the cation ordering. The compound undergoes a second order
transition
to a tetragonal structure, the transition temperature
being estimated
as 360degreesC.
2003-83
Ciurchea, D
Structure and superconducting properties of (Bi,Pb): 2223
superconductor with 3D excess conductivity
INTERNATIONAL JOURNAL OF MODERN PHYSICS B 17, 2003, 2851-2861.
The full pattern decomposition method by Le Bail was applied to a
single phase orthorhombic (Bi,Pb):2223 superconductor
with an
accentuated three dimensional excess conductivity The
space group Pmam,
with the lattice parameters a = 5.2598, b = 5.5381, c
= 37.174 Angstrom
was found. The Fourier maps derived show that delocalization
of the Sr
atoms induces terracing of the Cu/Ca/Cu superconducting
stacking of 0.3
Angstrom, close to the c-axis coherence length, yielding
the three
dimensional character of the conduction evidenced by the
resistivity
measurements.
2003-84
Coste, S Gautier, E Evain, M Bujoli-Doeuff,
M Brec, R
Jobic, S Kanatzidis, MG
NaV1-xP2S6 (x=0.16): A new compound with infinite straight
(1/infinity)[V0.837P2S6](-) chains that exfoliate forming
gels
CHEMISTRY OF MATERIALS 15, 2003, 2323-2327.
The new 1D chalcogenophosphate material NaV0.837(6)P2S6 has been
synthesized and its structure determined by X-ray powder
diffraction
analysis. This compound crystallizes in the monoclinic
space group
P2(1)/n with a = 6.9677(3) Angstrom, b = 5.9059(2) Angstrom,
c =
21.4537(s) Angstrom, and beta = 92.962(2)degrees [Z =
4, V = 881.66(8)
Angstrom(3)]. The Rietveld refinement led to R-p/R-wp
= 0.0208/0.0271
(for 94 parameters refined). The material is isostructural
with
1D-NaCrP2S6 and contains infinite (1/infinity)[V0.837(6)P2S6](_)
chains
consisting of randomly occupied edge-sharing [VS6] octahedra
defining
zigzag (1/infinity)[VS4] ribbons that are capped by tetradendate
[P2S6]
ethane-like groups linked to three successive [VS6] polyhedra.
Because
of the nonstoichiometry of the phase, the charge balance
can be written
as Na+(V4+)(0.486)(V3+)(0.351)(P4+)(2)(S2-)(6). NaV0.837(6)P2S6
is
soluble in strongly polar organic solvents such as N-methylformamide
(NMF). The exfoliation of NaV0.837(6)P2S6 in NMF leads
to gels or to
colored colloidal solutions with complex fluid behavior
that depends
strongly on concentration.
2003-85
Dinnebier, RE Vensky, S Panthofer, M
Jansen, M
Crystal and molecular structures of alkali oxalates: First proof of
a
staggered oxalate anion in the solid state
INORGANIC CHEMISTRY 42, 2003, 1499-1507.
The molecular and crystal structures of solvent-free potassium,
rubidium, and cesium oxalates have been determined ab
initio from
high-resolution synchrotron and X-ray laboratory powder
patterns. In
the case of potassium oxalate K2C2O4 (a = 10.91176(7)
Angstrom, b =
6.11592(4) Angstrom, c 3.44003(2) Angstrom, orthorhombic,
Pbam, Z = 2),
the oxalate anion is planar, whereas in cesium oxalate
Cs2C2O4 (a =
6.62146(5) Angstrom, b = 11.00379(9) Angstrom, c = 8.61253(7)
Angstrom,
beta = 97.1388(4)degrees, monoclinic, P2(1)/c, Z = 4)
it exhibits a
staggered conformation. For rubidium oxalate at room temperature,
two
polymorphs exist, one (beta-Rb2C2O4) isotypic to potassium
oxalate (a =
11.28797(7) Angstrom, b = 6.29475(4) Angstrom, c = 3.62210(2)
Angstrom,
orthorhombic, Pbam, Z 2) and the other (alpha-Rb2C2O4)
isotypic to
cesium oxalate (a = 6.3276(1) Angstrom, b = 10.4548(2)
Angstrom, c =
8.2174(2) Angstrom, beta = 98.016(1)degrees, monoclinic,
P2(1)/c, Z =
4). The potassium oxalate structure can be deduced from
the AlB2 type,
and the cesium oxalate structure from the Hg99As type,
respectively.
The relation between the two types of crystal structures
and the reason
for the different conformations of the oxalate anion are
discussed.
2003-86
Wunschel, M Dinnebier, RE Carlson, S
Bernatowicz, P van Smaalen, S
Influence of the molecular structures on the high-pressure and
low-temperature phase transitions of plastic crystals
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 59, 2003, 60-71.
The crystal structures of tert-butyl-tris(trimethylsilyl)silane,
Si[C(CH3)(3)](1) [Si(CH3)(3)](3) (Bu1), and
di-tert-butyl-bis(trimethylsilyl)silane, Si[C(CH3)(3)](2)
[Si(CH3)(3)](2) (Bu2), at room temperature and at 105
K have been
determined by X-ray powder diffraction; the high-pressure
behavior for
pressures between 0 and 5 GPa is reported. The room-temperature
structures have cubic Fm (3) over barm symmetry (Z = 4)
with a =
13.2645 (2) Angstrom, V = 2333.87 (4) Angstrom(3) for
Bu1 and a =
12.9673 (1) Angstrom, V = 2180.46 (3) Angstrom(3) for
Bu2. The
molecules are arranged in a cubic close packing (c.c.p.)
and exhibit at
least 48-fold orientational disorder. Upon cooling both
compounds
undergo a first-order phase transition at temperatures
T c = 230 (5) K
(Bu1) and Tc = 250 (5) K (Bu2) into monoclinic structures
with space
group P2(1)/n. The structures at 105 K have a = 17.317
(1), b = 15.598
(1), c = 16.385 (1) Angstrom, gamma = 109.477 (4)degrees,
V = 4172.7
(8) Angstrom(3) and Z = 8 for Bu1 and a = 17.0089 (9),
b = 15.3159 (8),
c = 15.9325 (8) Angstrom, gamma = 110.343 (3)degrees,
V = 3891.7 (5)
Angstrom(3) and Z = 8 for Bu2. The severe disorder of
the
room-temperature phase is significantly decreased and
only a two- or
threefold rotational disorder of the molecules remains
at 105 K.
First-order phase transitions have been observed at pressures
of
0.13-0.28 GPa for Bu1 and 0.20-0.24 GPa for Bu2. The high-pressure
structures are isostructural to the low-temperature structures.
The
pressure dependencies of the unit-cell volumes were fitted
with Vinet
equations of state and the bulk moduli were obtained.
At still higher
pressures further anomalies in the pressure dependencies
of the lattice
parameters were observed. These anomalies are explained
as additional
disorder-order phase transitions.
2003-87
Asthalter, T Franz, H van Burck, U
Messel, K Schreier, E Dinnebier, R
Structure and dynamics of octamethyl-ethinyl-ferrocene: an
organometallic rotator phase
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 64, 2003, 677-684.
The onset of dynamics and the structural changes of
octamethyl-ethinyl-ferrocene around a solid-solid phase
transition at
248 K have been investigated using the novel technique
of quasielastic
nuclear forward scattering (QNFS) in a temperature range
between 61 and
257 K at a photon energy of 14.413 keV, as well as X-ray
powder
diffraction at various energies. A pronounced hysteresis
for both the
dynamical and the structural properties is observed and
confirmed by
differential-scanning calorimetry. We assign the observed
phenomena to
a first-order transition from a low-symmetry low-temperature
phase to a
high-symmetry high-temperature plastically crystalline
phase with
nearly cubic symmetry. Possible mechanisms for this transition
are
discussed in the light of our results.
2003-88
Harvey, HG Hu, J Attfield, MP
Synthesis, structural characterization, and readsorption behavior of
a
solid solution aluminum phosphite/ethylenediphosphonate
series
CHEMISTRY OF MATERIALS 15, 2003, 179-188.
Members of the new solid solution aluminum phosphite/
ethylenediphosphonate series,
Al-2[(O3PC2H4PO3)(1-x)(HPO3)(2x)](H2O)(2)F-2 . H2O (0
less than or
equal to x less than or equal to 0.32), have been prepared
and fully
characterized. The full dehydration behavior of the parent
material of
this series, Al-2[O-3-PC2H4PO3](H2O)(2)F-2.H2O (x = 0)
has been
resolved. On heating the material to 230 degreesC the
extraframework
water is the primary species desorbed and the framework
structure
remains intact as determined from the crystal structure
of the
partially dehydrated material, Al-2[O3PC2H4Po3](H2O)(2)F-2.0.51(3)H2O.
Above 150 degreesC, but more noticeably above 200 C, framework
water is
lost, resulting in the formation of 4- and 5-coordinated
Al centers. By
340 degreesC all the framework water and some fluorine
is lost
resulting in the collapse of the crystalline material.
The phosphite
substituted materials (0 less than or equal to x less
than or equal to
0.32) are shown, by diffraction and spectroscopic techniques,
to be
single-phase solid solutions. Rietveld refinement of the
structure of
the x = 0.19 member reveals that a random substitution
of phosphite
groups for diphosphonate species exists throughout the
bulk of the
material and that the remainder of the framework remains
unaltered by
incorporation of this moiety. The readsorption behavior
of the
materials (0 less than or equal to x less than or equal
to 0.32)
indicates that the temperature at which the extraframework
water is
first removed decreases as x increases and that the amount
of water
lost and degree of readsorption increase as x increases.
These results
indicate that the porosity of the materials can be controlled
in a
manner conducive to their rational design.
2003-89 ???
Allen, S Warmingham, NR Gover, RKB
Evans, JSO
Synthesis, structure and thermal contraction of a new low-temperature
polymorph of ZrMo(2)(O)8
CHEMISTRY OF MATERIALS 15, 2003, 3406-3410.
2003-90
Meejoo, S Kariuki, BM Kitchin, SJ
Cheung, EY Albesa-Jove, D Harris, KDM
Structural aspects of the beta-polymorph of (E)-4-formylcinnamic acid:
Structure determination directly from powder diffraction
data and
elucidation of structural disorder from solid-state NMR
HELVETICA CHIMICA ACTA 86, 2003, 1467-1477.
Among the derivatives of (E)-cinnamic acid for which the solid-state
photochemical properties have been studied, (E)-4-formylcinnamic
acid
(1) has already received much attention. Given the inability
to prepare
single crystals of the beta-polymorph of 1 that are of
suitable size
and quality for structural characterization by single-crystal
X-ray
diffraction, the structure of this material was determined
directly
from powder X-ray-diffraction data by means of the genetic-algorithm
technique for structure solution, followed by Rieveld
refinement.
High-resolution solid-state C-13-NMR was also applied
to elucidate
details of structural disorder concerning the orientation
of the formyl
group, and provided independent support for the disorder
model
established form the Rietveld refinement. The reported
structure
establishes that the beta-phase of 1 is not structurally
anomalous
among photoreactive (E)-cinnamic acid crystals, and finally
resolves a
long-standing controversy concerning the structural properties
of this
material.
2003-91
Mora, AJ Fitch, AN Ramirez, BM
Delgado, GE Brunelli, M Wright, J
Structure of lithium benzilate hemihydrate solved by simulated
annealing and difference Fourier synthesis from powder
data
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE 59, 2003, 378-383.
The crystal structure of lithium benzilate hemihydrate
(C14H11O3-Li+.0.5H(2)O) was solved from synchrotron powder
diffraction
data. This compound crystallizes in the monoclinic space
group P2(1)/a.
The structure was solved via the direct space search for
two benzilate
fragments using the simulated-annealing program DASH,
localization of
the lithium ions and water molecule from a difference
Fourier map, and
a restrained Rietveld refinement (R-wp = 0.0687). The
structure is a
coordination polymer of [Li-2(C14H11O3) (2).H2O](2) tetramers
building
helical fourfold one-dimensional channels parallel to
[010]. Inside the
channels the tetrahedral coordination spheres of the lithium
ions
contain hydroxyl and carbonyl groups, and water molecules.
The water
molecule functions as the cohesive entity forming extended
hydrogen-bonded chains running along [010], and bifurcated
donor
hydrogen bonds with the two nearest carboxylates. At the
outer edge of
the channels, weaker intermolecular C-H...Ph hydrogen
bonds along [100]
and [001] contribute to the supramolecular aggregation
of the structure.
2003-92
Dinnebier, R Muller, J
New insights into an old reaction. High-resolution X-ray powder
diffraction of Wiberg's aminoalane intermediate
INORGANIC CHEMISTRY 42, 2003, 1204-1210.
In accordance with the procedure described by E. Wiberg, Me3Al-NH3
was
heated as a bulk material in inert atmosphere to give
a colorless
liquid which slowly loses methane. Close to the end of
this elimination
reaction, the melt crystallized to give a microcrystalline
powder of
(Me2AlNH2)(x). The structure of this intermediate has
been solved by
the method of high-resolution X-ray powder diffraction.
The compound
crystallizes in the monoclinic space group C2/c with the
cell
parameters of a = 15.0047(6) Angstrom, b = 8.7500(2) Angstrom,
c =
24.4702(8) Angstrom, and beta = 107.290(2)degrees, with
eight trimers
(Me(2)AINH(2))(3) Per unit cell. These trimers crystallize
in a boat
conformation in contrast to the known trimers of the same
composition
where a twist-boat conformation had been found by single
crystal
determination. Different conformers of (Me2AINH2)3 have
been
investigated by theoretical methods (HF/6-31G(d), B3LYP/6-31
G(d),
B3LYP/6-311G(d,p), MP2(fc)/6-31 G(d), and MP2(fc)/6-311G(d,p)).
The
twist-boat and the chair conformer correspond to minima
at the
potential energy surface, whereas the boat conformer corresponds
to a
first-order transition state (relative energies of 0.45-2.56
kJ/mol
(boat) and 6.66-11.91 kJ/mol (chair)). Relaxed scans of
the potential
energy surface at the HF/6-31G(d) and B3LYP/6-31G(d) levels
have shown
that the boat conformer (C-s symmetry) connects two enantiomers
of the
twist-boat form (C-2 symmetry).
2003-94
Jorgensen, JD Avdeev, M Hinks, DG
Burley, JC Short, S
Crystal structure of the sodium cobaltate deuterate superconductor
NaxCoO2 . 4xD(2)O (x approximate to 1/3)
PHYSICAL REVIEW B 68, iss 21, 2003, 214517
Neutron and x-ray powder diffraction have been used to investigate
the
crystal structures of a sample of the newly-discovered
superconducting
sodium cobaltate deuterate compound with composition
Na0.31(3)CoO2.1.25(2)D2O and its anhydrous parent compound
Na0.61(1)CoO2. The anhydrous parent compound Na0.61(1)CoO2
has two
partially occupied Na sites sandwiched, in the same plane,
between CoO2
layers. When Na is removed to make the superconducting
composition, the
Na site that experiences the strongest Na-Co repulsion
is emptied while
the occupancy of the other Na site is reduced to about
one third. The
deuterate superconducting compound is formed by coordinating
four D2O
molecules (two above and two below) to each remaining
Na ion in a way
that gives Na-O distances nearly equal to those in the
parent compound.
One deuteron of the D2O molecule is hydrogen bonded to
an oxygen atom
in the CoO2 plane and the oxygen atom and the second deuteron
of each
D2O molecule lie approximately in a plane between the
Na layer and the
CoO2 layers. This coordination of Na by four D2O molecules
leads in a
straightforward way to ordering of the Na ions and D2O
molecules
consistent with the observation of additional shorter-range
scattering
features in the diffraction data. The sample studied here,
which has
T-c=4.5 K, has a refined composition of Na0.31(3)CoO2.1.25(2)D2O,
in
agreement with the expected 1:4 ratio of Na to D2O. These
results show
that the optimal superconducting composition should be
viewed as a
specific hydrated compound, not a solid solution of Na
and D2O (H2O) in
NaxCoO2.D2O. The hydrated superconducting compound may
be stable over a
limited range of Na and D2O concentration, but studies
of T-c and other
physical properties vs Na or D2O composition should be
viewed with
caution until it is verified that the compound remains
in the same
phase over the composition range of the study.
2003-95
Jurgens, B Irran, E Senker, J Kroll,
P Muller, H Schnick, W
Melem (2,5,8-triamino-tri-s-triazine), an important intermediate during
condensation of melamine rings to graphitic carbon nitride:
Synthesis,
structure determination by X-ray powder diffractometry,
solid-state
NMR, and theoretical studies
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125, 2003, 10288-10300.
Single-phase melem (2,5,8-triamino-tri-s-triazine) C6N7(NH2)(3) was
obtained as a crystalline powder by thermal treatment
of different less
condensed C-N-H compounds (e.g., melamine C3N3(NH2)(3),
dicyandiamide
H4C2N4, ammonium dicyanamide NH4[N(CN)(2)], or cyanamide
H2CN2,
respectively) at temperatures up to 450 degreesC in sealed
glass
ampules. The crystal structure was determined ab initio
by X-ray powder
diffractometry (Cu Kalpha(1): P2(1)/c (No. 14), a = 739.92(1)
pm, b =
865.28(3) pm, c = 1338.16(4) pm, beta = 99.912(2)degrees,
and Z = 4).
In the solid, melem consists of nearly planar C6N7(NH2)(3)
molecules
which are arranged into parallel layers with an interplanar
distance of
327 pm. Detailed C-13 and N-15 MAS NMR investigations
were performed.
The presence of the triamino form instead of other possible
tautomers
was confirmed by a CPPI (cross-polarization combined with
polarization
inversion) experiment. Furthermore, the compound was characterized
using mass spectrometry, vibrational (IR, Raman), and
photoluminescence
spectroscopy. The structural and vibrational properties
of molecular
melem were theoretically studied on both the B3LYP and
the MP2 level. A
structural optimization in the extended state was performed
employing
density functional methods utilizing LDA and GGA. A good
agreement was
found between the observed and calculated structural parameters
and
also for the vibrational frequencies of melem. According
to
temperature-dependent X-ray powder diffractometry investigations
above
560 degreesC, melem transforms into a graphite-like C-N
material.
2003-96
Hauback, BC Brinks, HW Jensen, CM
Murphy, K Maeland, AJ
Neutron diffraction structure determination of NaAlD4
JOURNAL OF ALLOYS AND COMPOUNDS 358, 2003, 142-145.
The structure of NaAlD4 has been determined from Rietveld-type
refinements of powder neutron diffraction data at 8 and
295 K. The
space group is I4(1) la with a = 501.19(l) and c = 1131.47(5)
pm at 295
K. The Na atoms are surrounded by eight D atoms from eight
different
[AlD4](-) tetrahedra in the geometry of a distorted square
antiprism.
The two different Na-D distances are nearly equal: 240.3(2)
and
240.5(2) pm at 8 K and 243.1(2) and 243.9(2) pm at 295
K. The Al-D
distance is 162.7(2) and 162.6(2) pm at 8 and 295 K, respectively.
2003-97
Cheung, EY Kitchin, SJ Harris, KDM
Imai, Y Tajima, N Kuroda, R
Direct structure determination of a multicomponent molecular crystal
prepared by a solid-state grinding procedure
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 125, 2003, 14658-14659.
2003-98
Schwarz, U Akselrud, L Rosner, H
Ormeci, A Grin, Y Hanfland, M
Structure and stability of the modulated phase Sb-II
PHYSICAL REVIEW B 67, 2003, iss 21, 214101.
The crystal structure of Sb-II has been determined using
angle-dispersive x-ray diffraction of synchrotron radiation.
The
crystal structure comprises an interpenetrating assembly
of a
tetragonal host sublattice with symmetry I422 and a tetragonal
guest
sublattice of symmetry I422, which realize common a axes
but different
c axes. Weak extra peaks that are also reported in recent
investigations performed independently are attributed
to modulation
waves of the atomic positions in both sublattices. A refinement
using
full profiles of powder-diffraction data was performed
in the
four-dimensional superspace group L--111(I422):L--111(I422).
The
structural investigation is accompanied by ab initio full-potential
band-structure calculations confirming the experimentally
determined
modification sequence. Fitting equations of state to the
results of
these computations generates pressure-volume relations
which are in
excellent agreement with the experimental data. On the
basis of
total-energy calculations, an earlier proposed crystal
structure of the
tetragonal phase has to be reconsidered in the light of
the composite
arrangement in Sb-II.
2003-99
Hummer, K Puschnig, P Ambrosch-Draxl, C
Ab initio study of anthracene under high pressure
PHYSICAL REVIEW B 67, 2003, iss 18, 184105.
The pressure effect on the internal molecular orientation, the
electronic and optical properties of crystalline anthracene
is
calculated up to 10.2 GPa by performing density-functional
calculations. As the only input for our ab initio calculations
we use
the lattice parameters experimentally determined by x-ray
powder
diffraction under pressure and optimize the internal geometry
with
respect to the three angles theta, chi, and delta, which
define the
orientation of the molecules inside the unit cell. For
the optimized
structures the isothermal bulk moduli, the electronic
band structures,
and dielectric tensors as a function of the unit-cell
volume are
calculated. The structure optimizations using the local-density
approximation and the generalized gradient approximation
exchange-correlation potentials give very similar results
and agree
well with the internal geometry determined from experiment.
This gives
rise to the conclusion that the application of such approximations
for
the description of organic molecular crystals within density-functional
theory is valid. Moreover, the electron distribution clearly
shows a
finite density between the molecules in the unit cell,
which increases
with pressure due to the enhancement of the intermolecular
interactions. These findings support the interpretation
that the
bonding mechanism in anthracene is not solely van der
Waals interaction.
2003-100
Lotsch, BV Senker, J Kockelmann, W
Schnick, W
Investigation of structural and dynamic properties of NH4[N(CN)(2)]
by
means of X-ray and neutron powder diffraction as well
as vibrational
and solid-state NMR spectroscopy
JOURNAL OF SOLID STATE CHEMISTRY 176, 2003, 180-191.
The crystal structure, spectroscopic and thermal properties of ammonium
dicyanamide NH4[N(CN)(2)] have been thoroughly investigated
by means of
temperature-dependent single-crystal X-ray and neutron
powder
diffraction, vibrational and MAS-NMR spectroscopy as well
as
thermoanalytical measurements. The comprehensive elucidation
of
structural details is of special interest with respect
to the unique
solid-state transformation of ammonium dicyanamide into
dicyandiamide.
This reaction occurs at temperatures >80degreesC and it
represents the
isolobal analogue of Wohler's historic transformation
of ammonium
cyanate into urea. NH4[N(CN)(2)] crystallizes in the monoclinic
space
group P2(1)/c with lattice constants a = 3.7913(8)1 b
= 12.412(2), c =
9.113(2) Angstrom, beta = 91.49(2)degrees and Z = 4 (single-crystal
X-ray data, T = 200 K). The temperature dependence of
the lattice
constants shows anisotropic behavior, however, no evidence
for phase
transitions in the investigated temperature range was
observed. The
hydrogen positions could be localized by neutron diffraction
(10-370
K), and the temperature-dependent behavior of the ammonium
group has
been analyzed by Rietveld refinements using anisotropic
thermal
displacement parameters. They were interpreted by utilizing
a rigid
body model and extracting the libration and translation
matrices of the
ammonium ion by applying the TLS formalism. The results
obtained by the
diffraction methods were confirmed and supplemented by
vibrational
spectroscopy and solid-state 1 5 N and C-13 MAS-NMR investigations.
2003-101
Pospisil, M Capkova, P Weissmannova, H
Klika, Z
Trchova, M Chmielova, M Weiss,
Z
Structure analysis of montmorillonite intercalated with rhodamine B:
modeling and experiment
JOURNAL OF MOLECULAR MODELING 9, 2003, 39-46.
The intercalation process and the structure of montmorillonite
intercalated with [rhodamine B](+) cations have been investigated
using
molecular modeling (molecular mechanics and molecular
dynamics
simulations), X-ray powder diffraction and IR spectroscopy.
The
structure of the intercalate depends strongly on the concentration
of
rhodamine B in the intercalation solution. The presence
of two phases
in the intercalated structure was revealed by modeling
and X-ray powder
diffraction: (i) phase with basal spacing 18 Angstrom
and with bilayer
arrangement of guests and (ii) phase with average basal
spacing 23
Angstrom and with monolayer arrangement of guests. In
both phases the
monomeric and dimeric arrangement can coexist in the interlayer
space.
Three types of dimers in the interlayer structure have
been found by
modeling: (i) H-dimer (head-to-head arrangement) present
in the 18
Angstrom phase, (ii) sandwich type of the head-to-tail
arrangement
(present in the 23 Angstrom phase) and (iii) J-dimer (head-to-tail
arrangement) present in the 23 Angstrom phase.
2003-102
Mairesse, G Roussel, P Vannier, RN
Anne, M Nowogrocki, G
Crystal structure determination of alpha-, beta- and gamma-Bi4V2O11
polymorphs. Part II: crystal structure of alpha-Bi4V2O11
SOLID STATE SCIENCES 5, 2003, 861-869.
The crystal structure of alpha-Bi4V2O11 was solved in the A2 space
group and refined using combined X-ray single crystal
and neutron
powder diffraction data in the following unit cell a =
16.5949(3)
Angstrom (3 x a(m) = 5.5316 Angstrom), b = 5.6106(1) Angstrom,
c =
15.2707(3) Angstrom, gamma = 90.260(2)degrees. It is built
upon
[Bi2O2](2+) layers spaced with vanadium-oxygen slabs where
the vanadium
atoms exhibit three different oxygen environments. The
main
characteristic of these V-O slabs is a well defined dimeric
unit with
two trigonal bipyramids sharing one edge and connected
to two VO
tetrahedra. These rigid blocks extend along [100] and
are spaced with a
disordered area where different V-O trigonal bipyramids
are
interconnected. A possible scheme to explain the actual
6a(m)
superlattice is proposed. It also accounts for the diffusion
lines
systematically observed along [100] by SAED. A relationship
between the
crystal structures of the three Bi4V2O11 polymorphs and
their
corresponding conductivity is tentatively suggested.
2003-103
Ouyang, X Tsai, TY Chen, DH Huang,
QJ Cheng, WH Clearfield, A
Ab initio structure study from in-house powder diffraction of a novel
ZnS(EN)(0.5) structure with layered wurtzite ZnS fragment
CHEMICAL COMMUNICATIONS iss 7, 2003, 886-887.
The solvothermal reaction of elemental zinc with sulfur in
ethylenediamine ( en) as solvent yields [ZnS.0.5(NH2CH2CH2NH2)],
1, an
unprecedented ethylenediamine pillared ZnS layered compound,
containing
two dimensional (2-D) boat-type 6-membered rings, which
was
characterized by ab initio structure solution from powder
diffraction
data (SDPD).
2003-104
Birkett, HE Cherryman, JC Chippendale, AM
Evans, JSO
Harris, RK James, M King, IJ
McPherson, GJ
Structural investigations of three triazines: solution-state NMR
studies of internal rotation and structural information
from
solid-state NMR, plus a full structure determination from
powder x-ray
diffraction in one case
MAGNETIC RESONANCE IN CHEMISTRY 41, 2003, 324-336.
Three model 2,4,6-tris(amino)-1,3, 5-triazines, structurally related
to
a dyestuff molecule previously studied by NMR, were synthesized
in
order to enable the effects of rotamer exchange on the
NMR spectra to
be investigated in more detail. Two of the compounds are
novel.
Internal rotation of the triazine ring substituents was
studied by
variable-temperature solution-state H-1, C-13 and N-15
NMR
spectroscopy. All the expected rotamers were detected
for each
molecule. Rotamer exchange rates varied from slow to fast
over the
temperature range -40 to 90degreesC, as observed for the
dyestuff
molecule itself. Solid-state C-13 and N-15 NMR provided
information
about the structures of the solid molecules. A full crystal
structure
determination from high-resolution powder x-ray diffraction
was
achieved for one of the molecules using simulated annealing
techniques.
Ab initio MO and N-15 NMR chemical shift calculations,
based on
energy-minimized structures derived from the x-ray structure
determination, enabled the effect of intermolecular hydrogen
bonding on
the N-15 NMR chemical shifts to be studied. The results
compared
favourably with the experimental solid-state N-15 NMR
shifts.
2003-105
Rocquefelte, X Boucher, F Gressier, P
Ouvrard, G
First-principle study of the intercalation process in the LixV2O5 system
CHEMISTRY OF MATERIALS 15, 2003, 1812-1819.
A theoretical study of the lithium intercalated LixV2O5 System has
been
performed using a dual approach, based on A initio calculations
and
experimental data. Two main aspects have been investigated:
the atomic
structure of each phase and the voltage of a lithium battery
with a
positive electrode made of LixV2O5. This approach leads
to proposal of
the full atomic arrangement for the different phases obtained
during
the reaction. Particularly, a structural arrangement is
proposed for
the debated omega-Li3V2O5 phase, based on a full simulation
of its
X-ray powder diagram. For the first time, an antiferromagnetic
ordering
is envisioned for xi-Li2V2O5. Finally, a very good simulation
of the
experimental open circuit voltage (OCV) curve of the battery,
from x =
0 to x = 3, is obtained when the magnetic interactions
are considered.
2003-106
Vors, JP Gerbaud, V Gabas, N Canselier,
JP Jagerovic, N
Jimeno, ML Elguero, J
The structure of the agrochemical fungicidal
4-chloro-3-(3,5-dichlorophenyl)-1H-pyrazole (RPA 406194)
and related
compounds
TETRAHEDRON 59, 2003, 555-560.
The difficulties to obtain convenient monocrystals of the important
fungicide RPA 406194 have been overcome by a combination
of solid state
C-13 NMR, X-ray powder diffraction and molecular modeling.
The
compound, a 3-aryl tautomer, crystallizes forming infinite
chains of
molecules bonded by N-H...N hydrogen bonds, leading to
needle-shaped
crystals. The tautomerism (equilibrium constant and energy
barrier) of
this compound in solution has been studied.
2003-107
Mairesse, G Roussel, P Vannier, RN
Anne, M Pirovano, C Nowogrocki, G
Crystal structure determination of alpha, beta and gamma-Bi4V2O11
polymorphs. Part I: gamma and beta-Bi4V2O11
SOLID STATE SCIENCES 5, 2003, 851-859.
Using combined X-ray single crystal and neutron powder
thermodiffraction data, the crystal structure of the high
temperature
gamma-form of Bi4V2O11 was confirmed and accurately refined
in the
I4/mmm space group and that of the beta-form was entirely
determined in
the centrosymmetric Amam space group. The two-fold superlattice
characterising the beta structure is the result of an
ordering process
involving corner-sharing V-O tetrahedra and disordered
trigonal
bipyramids. A possible scheme for the gamma <---->
beta phase
transition is proposed.
2003-108
Wallwork, KS Pring, A Taylor, MR
Hunter, BA
A model for the structure of the hydrated aluminum phosphate, kingite
determined by ab initio powder diffraction methods
AMERICAN MINERALOGIST 88, 2003, 235-239.
The crystal structure of kingite, Al-3(PO4)(2)(F,OH)(2).8(H2O,OH),
a
secondary mineral from a Cambrian-Precambrian phosphate
deposit at
Tom's Quarry, near Kapunda, South Australia, has been
determined from a
powder sample using synchrotron X-ray diffraction data.
The structure
was determined ab initio by direct methods and refined
to R-Bragg =
0.022 and R-wp = 0.039 using the Rietveld method. The
triclinic
structure was solved and refined in the space group P
(1) over bar1, a
= 9.377(1), b = 10.113(1), c = 7.138(1) Angstrom, alpha
= 97.60(1),
beta = 100.88(1), gamma = 96.01(1)degrees, V = 653.0(1)
Angstrom(3), Z
= 2. The structure of kingite contains finite strings
of three corner
sharing Alphi(6) octahedra (where phi represents O, OH-,
F-, or H2O).
These strings are cross-linked via PO4 tetrahedra to produce
layers
that are perpendicular to [100]. The layers are linked
via hydrogen
bonding through H2O located in the interlayer space. Kingite
is shown
to have a different stoichiometry to that reported earlier.
The
relationship of kingite to the structures of wavellite,
Al-3(PO4)(2)(OH)(3).5H(2)O, and mitryaevaite,
Al-5(PO4)(2)[(P,S)O-3(OH,O)](2)F-2(OH)(2)(H2O)(8).6.48H(2)O,
are
briefly discussed.
2003-109
Serre, C Ferey, G
Synthesis and structure determination from powder data of the first
organically templated tin(IV) phosphate: MIL-76 or
(Sn3O2)-O-IV(H2O)(HPO4)(4).{H2N-C2H4-NH2}(2.5.){H2O}(2)
CHEMICAL COMMUNICATIONS iss 15, 2003, 1818-1819.
The first organically templated tin(IV) phosphate has been isolated
and
its structure solved from powder X-ray diffraction data;
it exhibits a
one-dimensional inorganic network built up from chains
of trimers of
tin( IV) octahedra on which phosphate tetrahedral groups
are grafted
interacting with water molecules and organic moieties.
2003-110
Mulagaleev, RF Soloviev, LA Blokhin, AI
Kirik, SD
Synthesis and structure of
[Pd(NH3)(4)][cis-Pd(NH3)(2)(SO3)(2)][Pd(NH3)(3)(SO3)]
. H2O
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY
new palladium compound 29, 2003, 256-260.
[Pd(NH3)(4)][cis-Pd(NH3)(2)(SO3)(2)][Pd(NH3)(3)(SO3)]
. H2O (I) was
synthesized and its structure was studied by X-ray powder
diffraction
method. In the course of the synthesis, the initial
trans-diamminesulfite anionic complex is transformed into
the
cis-configuration. Further heating in aqueous solution
results in
isomerization of a substance into a neutral complex [Pd(NH3)(3)(SO3)].
Crystals I are triclinic: a = 10.3297(2) Angstrom, b =
14.1062(3)
Angstrom, c = 6.853 1(1) Angstrom, alpha = 101.36(0)degrees,
beta =
92.74(0)degrees, gamma = 92.71(0)degrees, space group
P (1) over bar.
Structure I consists of the columns with alternating
cis-[pd(NH3)(2)(SO3)(2)](2-) and [Pd(NH3)(3)(SO3)] complexes
and
[Pd(NH3)(4)](2+) ions between the columns.
2003-111
Ouyang, X Tsai, TY Chen, DH Huang,
QJ Cheng, WH Clearfield, A
Ab initio structure study from in-house powder diffraction of a novel
ZnS(EN)(0.5) structure with layered wurtzite ZnS fragment
(pg 886, 2003)
CHEMICAL COMMUNICATIONS iss 9, 2003, 1107-1107
2003-112
Laco, JII
Structural studies of poly[(2S,3S)-2,3-dimethoxybutylene alkanamide]s
POLYMER 44, 2003, 1935-1940.
The structural characterization of a series of stereoregular polyamides
4,n (n = 8, 10, 12), which were obtained from polycondensation
of
(2S,3S)-2,3-dimethoxy-1,4-butanediamine with aliphatic
dicarboxylic
acids, has been carried out. X-ray diffraction of powder
and fiber
samples were analyzed together with electron diffraction
patterns of
single crystals obtained by isothermal crystallization
in solution.
Experimental results based on lattice parameters data
were used to
build a preliminary crystal model using the Cerius program.
The main
characteristic of the proposed model is the presence of
intermolecular
hydrogen bonds along the crystal a direction, similarly
arranged to
conventional nylons.
2003-113
Celotti, G Landi, E
A misunderstood member of the nagelschmidtite family unveiled:
structure of Ca5Na2(PO4)(4) from X-ray powder diffraction
data
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 23, 2003, 851-858.
During the development of procedures to synthesize carbonate
hydroxyapatite with properties resembling those of biological
material,
a new phase was found to form after high temperature treatments
in the
presence of sodium. The compound was isolated and analytically
characterized, leading to its identification as Ca5Na2(PO4)(4):
an
analogous Ca-Na phosphate was previously described, but
with rather
poor diffraction data and uncertain stoichiometry. Accurate
XRD powder
patterns revealed a hexagonal cell, space group P6(3)mc
(186), a =
10.64 Angstrom, c = 21.71 Angstrom, Z = 6, rho = 2.93
g/cm(3), with the
a axis double and the c axis triple those of the subcell
typical of
alpha-phases in the well-known system A(2)XO(4) (or ABXO(4)).
The
complete structural determination was carried out and
the relevant
aspects and properties discussed.
2003-114
Grzywa, M Rafalska-Lasocha, A Lasocha, W
X-ray powder diffraction data of potassium
mu-oxo-bis(oxodiperoxovanadate)(4-) hydrate K-4[O{VO(O-2)(2)}(2)]H2O
POWDER DIFFRACTION 18, 2003, 248-251.
The potassium mu-Oxo-bis(oxodiperoxovanadate)(4-) hydrate
K-4[O{VO(O-2)(2)}(2)]*H2O was prepared, and its X-ray
powder
diffraction patterns have been recorded at room temperature.
The unit
cell parameters were refined to a=6.7097(1)Angstrom,
b=9.9574(1)Angstrom, c=15.8250(3)Angstrom, beta=93.69(6)degrees,
space
group P2(1)/c (14). The sample of K4V2O11*H2O was characterized
by IR
spectroscopy and analytical investigation. Results of
crystal structure
refinement by Rietveld method are presented; final R-F
and R-wp are 13
and 16%, respectively.
2003-115
Wunschel, M Dinnebier, RE Carlson, S
Van Smaalen, S
High-pressure phase transitions in tetrakis(trimethylsilyl)silane
Si[Si(CH3)(3)](4)
HIGH PRESSURE RESEARCH 23, 2003, 425-437.
The compound tetrakis(trimethylsilyl)silane S-i[Si(CH3,)(3)](4) (TSi)
has been studied at room temperature for pressures up
to 2 1.5(1) GPa,
using X-ray powder diffraction with synchrotron radiation.
Three
different phases are reported in the investigated pressure
range. The
c.c.p.-type structure is stable up to a pressure of 0.19(1)
GPa (Fm (3)
over barm, a = 13.52110)Angstrom, V = 2471.95(1)Angstrom(3),
Z = 4 at
0.02(1)GPa). It shows a severe orientational disorder
of the molecules.
At pressures 0.19(1)-0.71(1)GPa a monoclinic phase (HP1)
is found with
space group P2(1)/n and Z=8 (a = 17.746(1)Angstrom, b
=
16.098(1)Angstrom, c= 16.871(1)Angstrom, gamma = 111.437(5)degrees
and
V = 4486.3(8) Angstrom(3) at 0.24(1)GPa). Another monoclinic
phase
(HP2) exists at pressures 0.52(1)-8.67(5)GPa. This phase
has a smaller
unit cell than the HP1 phase with Z(.)=2 (a =8.3778(8)Angstrom,
b=9.1050(7)Angstrom, c= 13.3024(8)Angstrom, gamma= 111.63(1)degrees
and
V = 943.22(6) Angstrom(3) at 1.73(2)GPa). The pressure
dependencies of
the unit-cell volumes are successfully described by Mumaghan
or
Vinet-type equations of state. The structures at different
pressures
and temperatures of TSi and related compounds are described
as
distorted superstructures of the c.c.p. arrangement. The
occurrence of
different superstructures is rationalized as the result
of an optimized
packing of ordered molecules of various shapes.
2003-116
Fantin, G Fogagnolo, M Bortolini, O
Masciocchi, N Galli, S Sironi, A
Polymorphism of dehydrocholic acid: crystal structure of the beta-phase
and guest-mediated solid phase conversion
NEW JOURNAL OF CHEMISTRY 27, 2003, 1794-1800.
Dehydrocholic acid may be obtained in two polymorphic forms: alpha
and
beta. The complete characterization and the crystal structure
of the
beta-phase (obtained by unconventional powder diffraction
methods) are
described and discussed. Conversion of the alpha-form
into the
thermodynamically more stable beta-polymorph may be obtained
through a
room temperature solvent-mediated process. On the other
hand,
transformation of the beta-form into the alpha-form is
realized through
two distinct pathways: via a temperature-mediated process
or as a
guest-mediated solid state conversion, without the intervention
of an
amorphous state. R-(+)-Methyl p-tolyl sulfoxide is the
guest of choice
for this unusual beta-to-alpha transformation.
2003-117
Barea, E Navarro, JAR Salas, JM
Masciocchi, N Galli, S Sironi, A
[Cu(4-oxopyrimidinate)(2) . nH(2)O]infinity: a robust sodalite
type metal-organic framework exhibiting a rich host-guest
chemistry
POLYHEDRON 22, 2003, 3051-3057.
Reaction of Cu2+ salts with 4-hydroxypyrimidine (4-Hpymo) in
water:ammonia (9:1) solutions at room temperature leads
to formation of
either [Cu(4-pymo)(2)(NH3)(2)(H2O)(2)] (1) or
[Cu(4-pymo)(2)(.)nH(2)O](infinity) (2), depending on which
crystal
nucleation process occurs. Selective formation of 2 is
possible by
using non-coordinating Et3N as a base. X-ray diffraction
analyses have
been performed in both cases showing that 1 is a mononuclear
compound
in which the heterocyclic ligands monodentately coordinate
the copper
ions through the N1 nitrogen atom. 2 is a 3D socialite
type open
framework, in which each 4-pymo ligand bridges two copper
ions through
both nitrogen atoms in the N,N'-exobidentate mode. Heating
1 at 110
degreesC in air generates an amorphous phase (2a), which
shows the same
chemical analysis and spectroscopic properties as dehydrated
2.
Crystalline [Cu(4-pymo)(2.)nH(2)O](infinity) (2), possesses
interesting
physico-chemical properties related to its porous nature.
Indeed, this
material reversibly absorbs N-2 and water vapour with
minimal
structural changes.
2003-118
Cerný, R. & Alami-Yadri, K.
Orthorhombic Yb5Si4 from synchrotron powder data
Acta Cryst. E59, 2003, i1-i3.