Acta Crystallographica Section B

Structural Science

Volume 52, Part 2 (April 1996)

Cover illustration: Reaction cavities for 2-cyanoethyl groups in cobaloxime complexes. Courtesy of K. Sawada, D. Hashizume, A. Sekine, H. Uekusa, K. Kato, Y. Ohashi, K. Kakinuma and Y. Ohgo.

research papers
books received

research papers

Acta Cryst. (1996). B52, 217-222 [doi:10.1107/S0108768195010330]

Crystal and magnetic structure of piezoelectric, ferrimagnetic and magnetoelectric aluminium iron oxide FeAlO₃ from neutron powder diffraction

F. Bouree, J. L. Baudour, E. Elbadraoui, J. Musso, C. Laurent and A. Rousset

Synopsis: Neutron diffraction, using FeAlO₃ polycrystalline samples at T = 30 K, reveals a classical Néel ferrimagnetism with strong `180 degrees Fe-O-Fe' superexchange antiferromagnetic interactions and an extremely weak spontaneous magnetization (0.38 ± 0.17 [mu] _B). Piezoelectricity originates in the bond arrangement on the tetrahedral sites.

Acta Cryst. (1996). B52, 223-231 [doi:10.1107/S0108768195010524]

X-ray structure refinement of (3 + 1)-dimensional incommensurate composite (1-x)Ta₂O₅.xWO₃, x = 0.1

S. Schmid, K. Fütterer and J. G. Thompson

Synopsis: The structure of the x = 0.1 member of the (1-x)Ta₂O₅.xWO₃ solid solution is described and compared with the structures of the x = 0.14 and x = 0.267 members.

Acta Cryst. (1996). B52, 232-238 [doi:10.1107/S0108768195010810]

Isotope effect on anharmonic thermal atomic vibration and refinement of ¹²C and ³C diamond

T. Yamanaka and S. Morimoto

Synopsis: The anharmonic thermal vibration of atoms of ¹³C_x¹²C_1-x and the isotope dependence of their lattice constant have been examined after [kappa] refinement.

Acta Cryst. (1996). B52, 239-250 [doi:10.1107/S0108768195010925]

Atomic displacement parameters for garnets: a lattice-dynamical evaluation

T. Pilati, F. Demartin and C. M. Gramaccioli

Synopsis: Lattice-dynamical calculation of atomic displacement parameters, IR and Raman spectra, and thermodynamic functions for natural garnets is shown. Evidence for disordered Mg and Fe atoms in pyrope and almandine, respectively, is given.

Acta Cryst. (1996). B52, 251-259 [doi:10.1107/S010876819501202X]

Theoretical study of the deformation densities of d electrons in K₂[PdCl₆] and K₂[PtCl₆] crystals

Y. Sakai, T. Oshibe and E. Miyoshi

Synopsis: The deformation densities of d electrons in K₂[PdCl₆] and K₂[PtCl₆] crystals were analyzed by theoretical calculations using embedded cluster models.

Acta Cryst. (1996). B52, 260-265 [doi:10.1107/S0108768195013310]

Structure and optical non-linearity of PbO.2B₂O₃

D. L. Corker and A. M. Glazer

Synopsis: The crystal structure of PbO.2B₂O₃ is described. Optical non-linearity measurements are also presented, which indicate that both phase-matchability and high non-linearity may be achieved by barium doping.

Acta Cryst. (1996). B52, 266-269 [doi:10.1107/S0108768195014443]

Structure of Mg₆SO₂(OH)₁₄ determined by micro single-crystal X-ray diffraction

E. Hamada, N. Ishizawa, F. Marumo, K. Ohsumi, Y. Shimizugawa, K. Reizen and T. Matsunami

Synopsis: The crystal structure of Mg₆SO₂(OH)₁₄ has been solved from single-crystal diffraction data collected on an extremely small crystal of dimensions ca 0.5 x 100 x 2.5 [mu] m³ with synchrotron radiation. The structure is based on a stack of zigzag sheets composed of MgO₆ octahedra.

Acta Cryst. (1996). B52, 270-276 [doi:10.1107/S0108768195010640]

Structural investigation of homonuclear Pt₂ and heteronuclear PdPt complexes containing a metal-metal bond bridged by hydrido and sulfido ligands

W. Clegg, M. Capdevila, P. González-Duarte and J. Sola

Synopsis: The disordered room-temperature structure and ordered low-temperature structure of [Pt₂( [mu] -H)( [mu] -S)(dppe)₂](PF₆) are reported, together with the room-temperature structure of the corresponding PtPd complex. NMR spectroscopy confirms the genuine heteronuclear nature of the mixed-metal complex.

Acta Cryst. (1996). B52, 277-286 [doi:10.1107/S0108768195008263]

Crystal and molecular structures of 3-acetyl-5-[2-(3-ethyl-2-benzothiazolidene)]ethylidenerhodanine and its lithium and sodium salts. Layered organic-inorganic structures

F. Nüesch, M. Grätzel, R. Nesper and V. Shklover

Synopsis: For the first time the J aggregation in the crystal of merocyanine dye is determined. The structure and stability of layered organic-inorganic structures with internal surfaces are discussed.

Acta Cryst. (1996). B52, 287-295 [doi:10.1107/S0108768195010615]

Structure at 200 and 298 K and X-ray investigations of the phase transition at 242 K of [NH₂(CH₃)₂]₃Sb₂Cl₉ (DMACA)

J. Zaleski and A. Pietraszko

Synopsis: Studies on the mechanism of ferro-paraelectric phase transitions in DMACA are described. Temperature changes of Sb-Cl bond lengths of up to 0.3 Å were observed and attributed to the deformation of the lone-electron pair on the Sb^''' atom caused by N-HCl hydrogen bonds.

Acta Cryst. (1996). B52, 296-302 [doi:10.1107/S0108768195010822]

Modification of crystal structure of ammonium Rochelle salt [NaNH₄(+)-C₄H₄O₆.4H₂O] owing to the replacement of NH₄ ions with K ions

E. Suzuki, T. Muta, R. Nozaki and Y. Shiozaki

Synopsis: Modification of the crystal structure of ammonium Rochelle salt owing to the replacement of NH₄ with K ions is studied at room temperature. Differences in the accommodation ratios and the environment of the two types of NH₄ ion sites are given.

Acta Cryst. (1996). B52, 303-313 [doi:10.1107/S0108768195011736]

Four polymorphs of a cobaloxime complex with different solid-state photoisomerization rates

K. Sawada, D. Hashizume, A. Sekine, H. Uekusa, K. Kato, Y. Ohashi, K. Kakinuma and Y. Ohgo

Synopsis: A quantitative relation has been obtained between the void space around the reactive group and the reaction rate in the photoisomerization of four crystal forms of a cobalt complex.

Acta Cryst. (1996). B52, 314-322 [doi:10.1107/S0108768195012213]

Structure of vanadocene in the temperature interval 108-357 K and the nature of the ring disorder

M. Yu. Antipin and R. Boese

Synopsis: Multi-temperature X-ray diffraction analysis of the vanadocene Cp₂V single crystal at 108, 170, 297 and 357 K shows that crystal disorder in this compound has a dynamic nature, and at 108 K the crystal structure of Cp₂V is ordered. A model of the disordering at higher temperatures is supposed.

Acta Cryst. (1996). B52, 323-327 [doi:10.1107/S0108768195012432]

Structure of ammonium hydrogen succinate above and below the phase transition around 170K

A. Hirano, Y. Kubozono, H. Maeda, H. Ishida and S. Kashino

Synopsis: No ordering of the H-atom positions in the short hydrogen bonds between hydrogen succinate ions occurs by the phase transition.

Acta Cryst. (1996). B52, 328-331 [doi:10.1107/S0108768195012808]

Structure of a twin initially solved from a partial data set: di--chlorobis-[di-n-butyldithiocarbamato]dipalladium

S. C. Nyburg

Synopsis: The monoclinic cell assigned to the twins is not primitive (leading to overlap of hkl with h = ±3n) as originally supposed, but B-centred. This was discovered using a partial data set from which both h = ±3n and (h + l) = 2n + 1 had been removed. Reflexions h = ±3n do not in fact overlap and were restored for full refinement.

Acta Cryst. (1996). B52, 332-343 [doi:10.1107/S010876819500838X]

Structural studies on monohalogenated derivatives of the phytohormone indole-3-acetic acid (auxin)

B. Nigovic, B. Kojic-Prodic, S. Antolic, S. Tomic, V. Puntarec and J. D. Cohen

Synopsis: Structural studies of natural chlorinated auxin, 4-chloroindole-3-acetic acid and other phenyl-substituted halogen derivatives, based on X-ray structure analysis and computational chemistry methods, are presented.

Acta Cryst. (1996). B52, 344-351 [doi:10.1107/S0108768195010500]

Structures of four o-nitrobenzonitriles

D. Britton and C. J. Cramer

Synopsis: Three substituted o-nitrobenzonitriles show incipient intramolecular nucleophilic attack of a nitro O atom on the electrophilic nitrile C atom.

Acta Cryst. (1996). B52, 352-356 [doi:10.1107/S0108768195010652]

Structure of 1,3,5,7-tetranitro-3,7-diazabicyclo-[3.3.0]octane. Structure solution from molecular packing analysis

H. L. Ammon, Z. Du, R. D. Gilardi, P. R. Dave, F. Forohar and T. Axenrod

Synopsis: Structure solution with the crystal structure prediction program MOLPAK, starting with a molecular mechanics geometry-optimized model, is described. An example of a polynitrodiazabicyclo[3.3.0]octane ring system is studied.

Acta Cryst. (1996). B52, 357-368 [doi:10.1107/S0108768195011025]

Effects of H/D substitution on thermal vibrations in piperazinium hexanoate-h₁₁,d₁₁

J. Luo, J. R. Ruble, B. M. Craven and R. K. McMullan

Synopsis: From neutron diffraction data collected at 15 K, mean-square nuclear displacements are obtained for the intramolecular H and D vibrations. The isotope effect is highly significant. For the hexanoate anion, normal-mode analysis using the force field from ab initio quantum mechanical calculations gives mean-square displacements for H and D which do not agree with the neutron diffraction results.

Acta Cryst. (1996). B52, 369-375 [doi:10.1107/S0108768195011293]

The crystal packing modes of three sterically overcrowded imidazole derivatives

C. André, P. Luger, S. Lotz and W.-P. Fehlhammer

Synopsis: 4-Cyclohexylamino-5-hydroxy-1,5-diphenyl- [Delta] ³-imidazolin-2-one crystallizes as a racemate, whereas the corresponding 4-tert-butylamino derivative occurs optically resolved.

Acta Cryst. (1996). B52, 376-383 [doi:10.1107/S0108768195012006]

The rare trans-syn thymine photodimers: structures of polyoxyethylene-linked bisthymines and the derived trans-syn thymine photodimers. Comparison of the stereochemistry before and after photodimerization

C. G. Suresh, B. P. Gangamani and K. N. Ganesh

Synopsis: The structural comparison of two trans-syn thymine photodimers with their respective parent compounds shows that the dimerization results in a strained geometry about the cyclobutane ring and a disturbed planarity of the thymines. The degree of such stereochemical changes, consequent to dimerization, depends on the nature of the linker backbone.

Acta Cryst. (1996). B52, 384-387 [doi:10.1107/S0108768195012286]

Structure of the charge-transfer salt 2,2',5,5'-tetraselenafulvalene-7,7,8,8-tetracyano-p-quinodimethane (TSeF-TCNQ)

P. W. R. Corfield and S. J. La Placa

Synopsis: The charge-transfer salt TSeF-TCNQ has the same segregated stack structure as TTF-TCNQ. Replacement of S by Se changes the relative importance of cation-cation and anion-anion stack interactions in the crystal.

books received

Acta Cryst. (1996). B52, 388 [doi:10.1107/S0108768196099855]