http://journals.iucr.org/b/issues/2012/04/00/isscontsbdy.html Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials publishes scientific articles related to the structural science of compounds and materials in the widest sense. Knowledge of the arrangements of atoms, including their temporal variations and dependencies on temperature and pressure, is often the key to understanding physical and chemical phenomena and is crucial for the design of new materials and supramolecular devices. Acta Crystallographica B is the forum for the publication of such contributions. Scientific developments based on experimental studies as well as those based on theoretical approaches, including crystal-structure prediction, structure-property relations and the use of databases of crystal structures, are published. en Copyright (c) 2012 International Union of Crystallography 2012-08-01 International Union of Crystallography International Union of Crystallography http://journals.iucr.org urn:issn:0108-7681 Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials publishes scientific articles related to the structural science of compounds and materials in the widest sense. Knowledge of the arrangements of atoms, including their temporal variations and dependencies on temperature and pressure, is often the key to understanding physical and chemical phenomena and is crucial for the design of new materials and supramolecular devices. Acta Crystallographica B is the forum for the publication of such contributions. Scientific developments based on experimental studies as well as those based on theoretical approaches, including crystal-structure prediction, structure-property relations and the use of databases of crystal structures, are published. text/html Acta Crystallographica Section B: Structural Science, Volume 68, Part 4, 2012 text yearly 6 2002-02-01T00:00+00:00 4 68 2012-08-01 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science 323 urn:issn:0108-7681 med@iucr.org August 2012 2012-08-01 http://journals.iucr.org/logos/rss10b.gif http://journals.iucr.org/b/issues/2012/04/00/isscontsbdy.html Still image http://scripts.iucr.org/cgi-bin/paper?sn5110 The system Bi2(n + 2)MonO6(n + 1) is described within the superspace formalism. Two superspace models are proposed for the different members of this family, depending on the parity of the parameter n. The superspace model for the odd members is constructed through the embedding of the cationic distribution of the member with n = 3, and the modification of a superspace model previously proposed for the compound Bi2MoO6. However, this model cannot be applied to the even members of the family. Performing the appropriate transformations, a suitable superspace model for the even members is obtained. The atomic structure of the different compounds of the family have been refined through the Rietveld method combining synchrotron X-ray and neutron powder diffraction data. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Bereciartua, P.J. Zuñiga, F.J. Perez-Mato, J.M. Petříček, V. Vila, E. Castro, A. Rodríguez-Carvajal, J. Doyle, S. 2012-06-28 doi:10.1107/S0108768112017478 International Union of Crystallography The system of flexible composition Bi2(n + 2)MonO6(n + 1) is described within the superspace formalism with two models, depending on the parity of the parameter n. EN superspace description X-ray and neutron powder diffraction systems of flexible composition The system Bi2(n + 2)MonO6(n + 1) is described within the superspace formalism. Two superspace models are proposed for the different members of this family, depending on the parity of the parameter n. The superspace model for the odd members is constructed through the embedding of the cationic distribution of the member with n = 3, and the modification of a superspace model previously proposed for the compound Bi2MoO6. However, this model cannot be applied to the even members of the family. Performing the appropriate transformations, a suitable superspace model for the even members is obtained. The atomic structure of the different compounds of the family have been refined through the Rietveld method combining synchrotron X-ray and neutron powder diffraction data. text/html Structure refinement and superspace description of the system Bi2(n + 2)MonO6(n + 1) (n = 3, 4, 5 and 6) text 4 68 2012-06-28 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 323 340 http://scripts.iucr.org/cgi-bin/paper?bp5040 The (3 + 1)-dimensional superspace approach is applied to describe and refine a series of sheared compounds related to layered high Tc superconducting oxides. Two commensurate members (m = 4, 5) of the 2212 stair-like [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] family of compounds, previously studied using single-crystal diffraction data, are analyzed. A common average unit cell has been identified and a composition-dependent modulation wavevector is proposed. The model is built using only three independent atomic domains, one for the metal atoms and two for the O atoms. The three Sr, Bi and Fe species are described using close-connected crenel-like functions forming a continuous atomic domain along the internal space. The two oxygen domains are represented by crenel functions and the displacive modulation functions are built up by Legendre polynomials recently implemented in the program JANA2006. Surprisingly, the results of the refinements show a striking similarity of the displacive modulations for the two compounds analyzed, indicating that a unique model can be used to describe the correlations between the atomic displacements of the 2212 stair-like series. This final model is then applied to predict the structure of new members of the family. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Elcoro, L. Pérez, O. Perez-Mato, J.M. Petříček, V. 2012-06-28 doi:10.1107/S0108768112018095 International Union of Crystallography Two commensurate members (m = 4, 5) of the 2212 stair-like family of compounds with the composition [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] have been analyzed and refined in the (3 + 1)-dimensional superspace framework. Both compounds are described by a unique model, including displacive modulations. The assumption of the validity of the proposed model for a range of compositions allows a realistic prediction of the structures of other members of the family. EN superspace approach superconducting oxides atomic domains The (3 + 1)-dimensional superspace approach is applied to describe and refine a series of sheared compounds related to layered high Tc superconducting oxides. Two commensurate members (m = 4, 5) of the 2212 stair-like [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] family of compounds, previously studied using single-crystal diffraction data, are analyzed. A common average unit cell has been identified and a composition-dependent modulation wavevector is proposed. The model is built using only three independent atomic domains, one for the metal atoms and two for the O atoms. The three Sr, Bi and Fe species are described using close-connected crenel-like functions forming a continuous atomic domain along the internal space. The two oxygen domains are represented by crenel functions and the displacive modulation functions are built up by Legendre polynomials recently implemented in the program JANA2006. Surprisingly, the results of the refinements show a striking similarity of the displacive modulations for the two compounds analyzed, indicating that a unique model can be used to describe the correlations between the atomic displacements of the 2212 stair-like series. This final model is then applied to predict the structure of new members of the family. text/html Unified (3 + 1)-dimensional superspace description of the 2212-type stair-like [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] family of compounds text 4 68 2012-06-28 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 341 355 http://scripts.iucr.org/cgi-bin/paper?kd5061 A detailed analysis of correlations between structural features and cation conductivity is performed for KAlO2 polymorphs in a wide temperature range of 300–1023 K. To explore the migration maps of K+ cations we have used neutron diffraction data for low- and high-temperature KAlO2 polymorphs and applied for the first time a novel algorithm based on the natural tiling concept and implemented it into the program package TOPOS. Five independent elementary channels for the K+ cation migration have been revealed whose cross-sections were found to be essentially different in the low-temperature form, indicating a high anisotropy of the cation conductivity. During the transition to the cubic high-temperature phase all five channels become equivalent with sharply increased cross-sections that account for the jump-like increase of the cation conductivity and gives rise to its three-dimensional character. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Voronin, V.I. Shekhtman, G.S. Blatov, V.A. 2012-07-17 doi:10.1107/S0108768112027462 International Union of Crystallography A detailed analysis of correlations between structural features and cation conductivity is performed for KAlO2 polymorphs in a wide temperature range of 300–1023 K. To explore the migration maps of K+ cations we have used neutron diffraction data and applied for the first time a novel algorithm based on the natural tiling concept and implemented it into the program package TOPOS. EN solid electrolytes neutron diffraction K+ cation migration map program package TOPOS A detailed analysis of correlations between structural features and cation conductivity is performed for KAlO2 polymorphs in a wide temperature range of 300–1023 K. To explore the migration maps of K+ cations we have used neutron diffraction data for low- and high-temperature KAlO2 polymorphs and applied for the first time a novel algorithm based on the natural tiling concept and implemented it into the program package TOPOS. Five independent elementary channels for the K+ cation migration have been revealed whose cross-sections were found to be essentially different in the low-temperature form, indicating a high anisotropy of the cation conductivity. During the transition to the cubic high-temperature phase all five channels become equivalent with sharply increased cross-sections that account for the jump-like increase of the cation conductivity and gives rise to its three-dimensional character. text/html The natural tiling approach to cation conductivity in KAlO2 polymorphs text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 356 363 http://scripts.iucr.org/cgi-bin/paper?eb5015 The structures of ternary oxides and chalcogenides of alkali metals are dissected in light of the extended Zintl–Klemm concept. This model, which has been successfully extended to other compounds different to the Zintl phases, assumes that crystal structures can be better understood if the cation substructures are contemplated as Zintl polyanions. This implies the occurrence of charge transfer between cations, even if they are of the same kind. In this article, the charge transfer between cations is even more illustrative because the two alkali atoms have different electronegativity, so that the less electropositive alkali metal and the O/S atom always form skeletons characteristic of the group 14 elements. Thus, partial structures of the zincblende-, wurtzite-, PbO- and SrAl2-type are found in the oxides/sulfides. In this work, such an interpretation of the structures remains at a topological level. The analysis also shows that this interpretation is complementary to the model developed by Andersson and Hyde which contemplates the structures as the intergrowth of structural slabs of more simple compounds. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Vegas, A. 2012-06-28 doi:10.1107/S0108768112021234 International Union of Crystallography The structure of ternary oxides and chalcogenides of alkali metals can be better understood by assuming the electron transfer between cations, in an extension of the Zintl–Klemm concept. EN alkali oxides alkali chalcogenides crystal chemistry extended Zintl–Klemm concept The structures of ternary oxides and chalcogenides of alkali metals are dissected in light of the extended Zintl–Klemm concept. This model, which has been successfully extended to other compounds different to the Zintl phases, assumes that crystal structures can be better understood if the cation substructures are contemplated as Zintl polyanions. This implies the occurrence of charge transfer between cations, even if they are of the same kind. In this article, the charge transfer between cations is even more illustrative because the two alkali atoms have different electronegativity, so that the less electropositive alkali metal and the O/S atom always form skeletons characteristic of the group 14 elements. Thus, partial structures of the zincblende-, wurtzite-, PbO- and SrAl2-type are found in the oxides/sulfides. In this work, such an interpretation of the structures remains at a topological level. The analysis also shows that this interpretation is complementary to the model developed by Andersson and Hyde which contemplates the structures as the intergrowth of structural slabs of more simple compounds. text/html On the charge transfer between conventional cations: the structures of ternary oxides and chalcogenides of alkali metals text 4 68 2012-06-28 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 364 377 http://scripts.iucr.org/cgi-bin/paper?gp5054 General aspects concerned with (001)-, (110)- and (111)-oriented superlattices (SLs) have been investigated. In particular, the symmetry of these systems have been derived and given in detail. As a test, the obtained data have been utilized to calculate electronic structures and gaps of a standard GaAs/AlAs system using an accurate version of the first principle full potential linear muffin-tin orbital (FPLMTO) method based on a local-density functional approximation (LDA). Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Touaa, Z. Sekkal, N. 2012-07-17 doi:10.1107/S0108768112030091 International Union of Crystallography The necessary crystallographic input data are given for electronic-structure calculations of supercells with the (111), (001) or (110) orientations. They are applied to calculations on GaAs/AlAs superlattices of different thicknesses. EN growth axes symmetry superlattice quantum well electronic structure General aspects concerned with (001)-, (110)- and (111)-oriented superlattices (SLs) have been investigated. In particular, the symmetry of these systems have been derived and given in detail. As a test, the obtained data have been utilized to calculate electronic structures and gaps of a standard GaAs/AlAs system using an accurate version of the first principle full potential linear muffin-tin orbital (FPLMTO) method based on a local-density functional approximation (LDA). text/html Crystallographic input data for (001)-, (110)- and (111)-oriented superlattices text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 378 388 http://scripts.iucr.org/cgi-bin/paper?hw5021 A sequence of four phases has been found for an acetonitrile-solvated co-crystal with 15-crown-5 of the nickel complex [acetonitrilediaqua-κ1O-nitrato-κ2O-nitratonickel(II)]. The structure could be determined at intervals of ca 10 K in the range 90–273 K because crystals remain single through the three transitions. In phase (I) (T ≥ ca 240 K; P21/m, Z′ = ½), there is extensive disorder, which is mostly resolved in phase (III) (ca 230–145 K; P21/c, Z′ = 1). Phase (IV) (ca 145–90 K, and probably below; P\overline 1, Z′ = 2) is ordered. Phase (II) (ca 238–232 K) is modulated, but the satellite reflections are too weak to allow the structure to be determined within its stability range by standard methods. Most crystals that were flash-cooled from room temperature to 90 K have a metastable P21, Z′ = 5 superstructure that (at least in a commensurate approximation) was identified as similar to the structure of phase (II) by comparison of reconstructed reciprocal-lattice slices and by analogy with the phase behavior of the very similar compound [Ni(H2O)6](NO3)2·(15-crown-5)·2H2O [Siegler et al. (2011). Acta Cryst. B67, 486–498]. In the phase (II) structure slab-like regions that are like the disordered phase (I) structure alternate with regions of similar shape and size that are like the more ordered phase (III) structure. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Siegler, M.A. Parkin, S. Brock, C.P. 2012-06-28 doi:10.1107/S0108768112018319 International Union of Crystallography Acetonitrilediaqua-κ1O-nitrato-κ2O-nitratonickel(II) 15-crown-5 acetonitrile solvate was studied by single-crystal X-ray diffraction at intervals of 10 K in the range 90–273 K as the crystal passed, without obvious damage, through three phase transitions. The phase sequence includes an intermediate modulated phase that seems to be a kind of striped hybrid of the phases stable at immediately higher and lower temperatures. EN four-phase sequence modulated phase phase sequence disorder A sequence of four phases has been found for an acetonitrile-solvated co-crystal with 15-crown-5 of the nickel complex [acetonitrilediaqua-κ1O-nitrato-κ2O-nitratonickel(II)]. The structure could be determined at intervals of ca 10 K in the range 90–273 K because crystals remain single through the three transitions. In phase (I) (T ≥ ca 240 K; P21/m, Z′ = ½), there is extensive disorder, which is mostly resolved in phase (III) (ca 230–145 K; P21/c, Z′ = 1). Phase (IV) (ca 145–90 K, and probably below; P\overline 1, Z′ = 2) is ordered. Phase (II) (ca 238–232 K) is modulated, but the satellite reflections are too weak to allow the structure to be determined within its stability range by standard methods. Most crystals that were flash-cooled from room temperature to 90 K have a metastable P21, Z′ = 5 superstructure that (at least in a commensurate approximation) was identified as similar to the structure of phase (II) by comparison of reconstructed reciprocal-lattice slices and by analogy with the phase behavior of the very similar compound [Ni(H2O)6](NO3)2·(15-crown-5)·2H2O [Siegler et al. (2011). Acta Cryst. B67, 486–498]. In the phase (II) structure slab-like regions that are like the disordered phase (I) structure alternate with regions of similar shape and size that are like the more ordered phase (III) structure. text/html [Ni(MeCN)(H2O)2(NO3)2]·(15-crown-5)·MeCN: detailed study of a four-phase sequence that includes an intermediate modulated phase text 4 68 2012-06-28 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 389 400 http://scripts.iucr.org/cgi-bin/paper?bp5042 A novel silver-containing compound, bis(benzylamino)silver(I) benzylcarbamate, with an unusual molecular structure is easily synthesized by the reaction of benzylammonium benzylcarbamate and silver oxide. It crystallizes in the triclinic crystal system with the space group P\bar 1 with a = 5.2006 (5), b = 14.6298 (15), c = 14.7246 (15) Å, α = 68.729 (2), β = 83.507 (2), γ = 85.412 (2)° and Z = 2. In the crystal, one Ag atom coordinates with the two amino groups in two benzylamine molecules, and there are no silver–silver and silver–oxygen interactions. The carboxylate groups take part in balancing the electric charge and forming hydrogen bonds. Both the compound and the starting material benzylammonium benzylcarbamate exhibit room-temperature solid-state emissions with the peaks at 300 and 406 nm, respectively. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Liu, J. Zeng, X. Li, H. 2012-07-17 doi:10.1107/S0108768112030212 International Union of Crystallography Bis(benzylamino)silver(I) benzylcarbamate contains silver atoms coordinated to two nitrogen atoms of amino groups from different benzylamine molecules; metal–oxygen interactions are absent in the crystal structure. The title compound exhibits fluorescence properties. EN silver-containing compound bis(benzylamino)silver(I) benzylcarbamate spectroscopic properties A novel silver-containing compound, bis(benzylamino)silver(I) benzylcarbamate, with an unusual molecular structure is easily synthesized by the reaction of benzylammonium benzylcarbamate and silver oxide. It crystallizes in the triclinic crystal system with the space group P\bar 1 with a = 5.2006 (5), b = 14.6298 (15), c = 14.7246 (15) Å, α = 68.729 (2), β = 83.507 (2), γ = 85.412 (2)° and Z = 2. In the crystal, one Ag atom coordinates with the two amino groups in two benzylamine molecules, and there are no silver–silver and silver–oxygen interactions. The carboxylate groups take part in balancing the electric charge and forming hydrogen bonds. Both the compound and the starting material benzylammonium benzylcarbamate exhibit room-temperature solid-state emissions with the peaks at 300 and 406 nm, respectively. text/html Synthesis, structure and spectroscopic properties of a novel compound bis(benzylamino)silver(I) benzylcarbamate text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 401 406 http://scripts.iucr.org/cgi-bin/paper?ps5016 Powder X-ray diffraction patterns of the commercial phase of l-arabinitol were recorded with a laboratory diffractometer. The starting structural model was found by a Monte-Carlo simulated annealing method. The final structure was obtained through Rietveld refinements with soft restraints on the interatomic bond lengths and bond angles. H atoms of hydroxyl groups were localized by minimization of the crystalline energy. The cell is triclinic with the space group P1 and contains two molecules. The crystalline cohesion is achieved by an important network of O—H...O hydrogen bonds. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Derollez, P. Guinet, Y. Affouard, F. Danède, F. Carpentier, L. Hédoux, A. 2012-07-17 doi:10.1107/S0108768112019994 International Union of Crystallography The crystal structure of l-arabinitol at room temperature was solved from its powder X-ray diffraction pattern. The starting structural model was found by the simulated annealing method. The structure was obtained through Rietveld refinements with soft restraints on the interatomic bond lengths and bond angles. The H atoms of hydroxyl groups were localized by a minimization of the crystalline energy. EN powder X-ray diffraction simulated annealing method pentitols Powder X-ray diffraction patterns of the commercial phase of l-arabinitol were recorded with a laboratory diffractometer. The starting structural model was found by a Monte-Carlo simulated annealing method. The final structure was obtained through Rietveld refinements with soft restraints on the interatomic bond lengths and bond angles. H atoms of hydroxyl groups were localized by minimization of the crystalline energy. The cell is triclinic with the space group P1 and contains two molecules. The crystalline cohesion is achieved by an important network of O—H...O hydrogen bonds. text/html Structure determination of l-arabinitol by powder X-ray diffraction text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 407 411 http://scripts.iucr.org/cgi-bin/paper?gp5051 The effect of pressure on dl-alanine has been studied by X-ray powder diffraction (up to 8.3 GPa), single-crystal X-ray diffraction and Raman spectroscopy (up to ∼ 6 GPa). No structural phase transitions have been observed. At ∼ 1.5–2 GPa, cell parameters b and c become accidentally equal to each other, but the space-group symmetry does not change. There is no phase transition between 1.7 and 2.3 GPa, contrary to what has been reported earlier [Belo et al. (2010). Vibr. Spectrosc. 54, 107–111]. The presence of the second phase transition, which was claimed to appear within the pressure range from 6.0 to 7.3 GPa (Belo et al., 2010), is also argued. The changes in the Raman spectra have been shown to be continuous in all the pressure ranges studied. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Tumanov, N.A. Boldyreva, E.V. 2012-07-17 doi:10.1107/S0108768112028972 International Union of Crystallography Structural changes in dl-alanine at pressures up to 8.3 GPa are not related to phase transitions. EN high pressure X-ray powder diffraction Raman spectroscopy alanine phase transition The effect of pressure on dl-alanine has been studied by X-ray powder diffraction (up to 8.3 GPa), single-crystal X-ray diffraction and Raman spectroscopy (up to ∼ 6 GPa). No structural phase transitions have been observed. At ∼ 1.5–2 GPa, cell parameters b and c become accidentally equal to each other, but the space-group symmetry does not change. There is no phase transition between 1.7 and 2.3 GPa, contrary to what has been reported earlier [Belo et al. (2010). Vibr. Spectrosc. 54, 107–111]. The presence of the second phase transition, which was claimed to appear within the pressure range from 6.0 to 7.3 GPa (Belo et al., 2010), is also argued. The changes in the Raman spectra have been shown to be continuous in all the pressure ranges studied. text/html X-ray diffraction and Raman study of dl-alanine at high pressure: revision of phase transitions text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 412 423 http://scripts.iucr.org/cgi-bin/paper?kd5063 The [4π + 4π] photodimerization process of the 9-substituted anthracene derivative crystalline 9-methylanthracene (9-MA) was investigated using time-resolved X-ray powder diffraction. The study was carried out in-situ using a CCD area detector. Sequential and parametric Rietveld refinement was applied for quantitative phase analysis. The results of traditional sequential Rietveld refinement showed that the evolution of the dimerization process can be described using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model. The parameters of the JMAK equation were obtained successfully by parametric Rietveld refinement and suggest that the reaction follows heterogeneous nucleation and one-dimensional growth with a decreasing nucleation rate. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Mabied, A.F. Müller, M. Dinnebier, R.E. Nozawa, S. Hoshino, M. Tomita, A. Sato, T. Adachi, S. 2012-07-17 doi:10.1107/S0108768112027450 International Union of Crystallography The kinetics of the 9-methylanthracene photodimerization reaction was examined by time-resolved powder diffraction using a CCD detector and parametric Rietveld refinement. EN time-resolved powder diffraction photodimerization parametric Rietveld refinement 9-methylanthracene The [4π + 4π] photodimerization process of the 9-substituted anthracene derivative crystalline 9-methylanthracene (9-MA) was investigated using time-resolved X-ray powder diffraction. The study was carried out in-situ using a CCD area detector. Sequential and parametric Rietveld refinement was applied for quantitative phase analysis. The results of traditional sequential Rietveld refinement showed that the evolution of the dimerization process can be described using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model. The parameters of the JMAK equation were obtained successfully by parametric Rietveld refinement and suggest that the reaction follows heterogeneous nucleation and one-dimensional growth with a decreasing nucleation rate. text/html A time-resolved powder diffraction study of in-situ photodimerization kinetics of 9-methylanthracene using a CCD area detector and parametric Rietveld refinement text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 424 430 http://scripts.iucr.org/cgi-bin/paper?gp5052 The antifungal drug 5-fluorocytosine (4-amino-5-fluoro-1,2-dihydropyrimidin-2-one) was cocrystallized with five complementary compounds in order to better understand its drug–receptor interaction. The first two compounds, 2-aminopyrimidine (2-amino-1,3-diazine) and N-acetylcreatinine (N-acetyl-2-amino-1-methyl-5H-imidazol-4-one), exhibit donor–acceptor sites for R22(8) heterodimer formation with 5-fluorocytosine. Such a heterodimer is observed in the cocrystal with 2-aminopyrimidine (I); in contrast, 5-fluorocytosine and N-acetylcreatinine [which forms homodimers in its crystal structure (II)] are connected only by a single hydrogen bond in (III). The other three compounds 6-aminouracil (6-amino-2,4-pyrimidinediol), 6-aminoisocytosine (2,6-diamino-3H-pyrimidin-4-one) and acyclovir [acycloguanosine or 2-amino-9-[(2-hydroxyethoxy)methyl]-1,9-dihydro-6H-purin-6-one] possess donor–donor–acceptor sites; therefore, they can interact with 5-fluorocytosine to form a heterodimer linked by three hydrogen bonds. In the cocrystals with 6-aminoisocytosine (Va)–(Vd), as well as in the cocrystal with the antiviral drug acyclovir (VII), the desired heterodimers are observed. However, they are not formed in the cocrystal with 6-aminouracil (IV), where the components are connected by two hydrogen bonds. In addition, a solvent-free structure of acyclovir (VI) was obtained. A comparison of the calculated energies released during dimer formation helped to rationalize the preference for hydrogen-bonding interactions in the various cocrystal structures. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Tutughamiarso, M. Wagner, G. Egert, E. 2012-07-17 doi:10.1107/S010876811202561X International Union of Crystallography Cocrystallization attempts with 5-fluorocytosine yielded eight cocrystals and two structures of a single compound. In six cocrystals, the expected heterodimers held together by two or three hydrogen bonds are present. Ab initio energy calculations helped to rationalize the intermolecular hydrogen-bonding patterns observed in the crystal structures. EN 5-fluorocytosine complementary hydrogen bonding drug–receptor interaction pharmaceutical cocrystal acyclovir The antifungal drug 5-fluorocytosine (4-amino-5-fluoro-1,2-dihydropyrimidin-2-one) was cocrystallized with five complementary compounds in order to better understand its drug–receptor interaction. The first two compounds, 2-aminopyrimidine (2-amino-1,3-diazine) and N-acetylcreatinine (N-acetyl-2-amino-1-methyl-5H-imidazol-4-one), exhibit donor–acceptor sites for R22(8) heterodimer formation with 5-fluorocytosine. Such a heterodimer is observed in the cocrystal with 2-aminopyrimidine (I); in contrast, 5-fluorocytosine and N-acetylcreatinine [which forms homodimers in its crystal structure (II)] are connected only by a single hydrogen bond in (III). The other three compounds 6-aminouracil (6-amino-2,4-pyrimidinediol), 6-aminoisocytosine (2,6-diamino-3H-pyrimidin-4-one) and acyclovir [acycloguanosine or 2-amino-9-[(2-hydroxyethoxy)methyl]-1,9-dihydro-6H-purin-6-one] possess donor–donor–acceptor sites; therefore, they can interact with 5-fluorocytosine to form a heterodimer linked by three hydrogen bonds. In the cocrystals with 6-aminoisocytosine (Va)–(Vd), as well as in the cocrystal with the antiviral drug acyclovir (VII), the desired heterodimers are observed. However, they are not formed in the cocrystal with 6-aminouracil (IV), where the components are connected by two hydrogen bonds. In addition, a solvent-free structure of acyclovir (VI) was obtained. A comparison of the calculated energies released during dimer formation helped to rationalize the preference for hydrogen-bonding interactions in the various cocrystal structures. text/html Cocrystals of 5-fluorocytosine. I. Coformers with fixed hydrogen-bonding sites text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 431 443 http://scripts.iucr.org/cgi-bin/paper?gp5053 Two flexible molecules, biuret and 6-acetamidouracil, were cocrystallized with 5-fluorocytosine to study their conformational preferences. In the cocrystal with 5-fluorocytosine (I), biuret exhibits the same conformation as in its hydrate. In contrast, 6-acetamidouracil can adopt two main conformations depending on its crystal environment: in crystal (II) the trans form characterized by an intramolecular hydrogen bond is observed, while in the cocrystal with 5-fluorocytosine (III), the complementary binding induces the cis form. Three cocrystals of 6-methylisocytosine demonstrate that complementary binding enables the crystallization of a specific tautomer. In the cocrystals with 5-fluorocytosine, (IVa) and (IVb), only the 3H tautomer of 6-methylisocytosine is present, whereas in the cocrystal with 6-aminoisocytosine, (V), the 1H tautomeric form is adopted. The complexes observed in the cocrystals are stabilized by three hydrogen bonds similar to those constituting the Watson–Crick C·G base pair. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Tutughamiarso, M. Egert, E. 2012-07-17 doi:10.1107/S0108768112029977 International Union of Crystallography Five cocrystals (four with 5-fluorocytosine and one with 6-aminoisocytosine) are presented to study the influence of complementary binding on conformational flexibility and the tautomeric equilibrium. EN drug–receptor interaction pharmaceutical cocrystal tautomeric equilibrium conformational change Two flexible molecules, biuret and 6-acetamidouracil, were cocrystallized with 5-fluorocytosine to study their conformational preferences. In the cocrystal with 5-fluorocytosine (I), biuret exhibits the same conformation as in its hydrate. In contrast, 6-acetamidouracil can adopt two main conformations depending on its crystal environment: in crystal (II) the trans form characterized by an intramolecular hydrogen bond is observed, while in the cocrystal with 5-fluorocytosine (III), the complementary binding induces the cis form. Three cocrystals of 6-methylisocytosine demonstrate that complementary binding enables the crystallization of a specific tautomer. In the cocrystals with 5-fluorocytosine, (IVa) and (IVb), only the 3H tautomer of 6-methylisocytosine is present, whereas in the cocrystal with 6-aminoisocytosine, (V), the 1H tautomeric form is adopted. The complexes observed in the cocrystals are stabilized by three hydrogen bonds similar to those constituting the Watson–Crick C·G base pair. text/html Cocrystals of 5-fluorocytosine. II. Coformers with variable hydrogen-bonding sites text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 444 452 http://scripts.iucr.org/cgi-bin/paper?ry5045 The single-crystal diffraction structures of 38 salt forms of the base tyramine (4-hydroxyphenethylamine) are reported for the first time. Together with literature examples, these structures are discussed with respect to cation conformation, cation packing, hydrogen bonding and hydrate formation. It is found that isostructural cation packing can occur even with structurally different anions, with different hydration states and with different hydrogen bonding. Hydrate formation is found to be more likely both (i) when there is an increase in the total number of potential hydrogen bond acceptor and donor atoms; and (ii) when the ratio of potential hydrogen bond donor to acceptor atoms is low. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Briggs, N.E.B. Kennedy, A.R. Morrison, C.A. 2012-07-17 doi:10.1107/S0108768112026456 International Union of Crystallography A structural study of 42 salt forms of the phenylethylamine tyramine examines cation conformation, cation packing and hydrogen bonding as well as showing that hydrate formation is favoured both by higher total numbers of potential hydrogen-bond acceptors and donors and by lower donor:acceptor ratios. EN dinuclear oxofluorometallates vibrational spectra bridging fluorine atoms merohedral twins The single-crystal diffraction structures of 38 salt forms of the base tyramine (4-hydroxyphenethylamine) are reported for the first time. Together with literature examples, these structures are discussed with respect to cation conformation, cation packing, hydrogen bonding and hydrate formation. It is found that isostructural cation packing can occur even with structurally different anions, with different hydration states and with different hydrogen bonding. Hydrate formation is found to be more likely both (i) when there is an increase in the total number of potential hydrogen bond acceptor and donor atoms; and (ii) when the ratio of potential hydrogen bond donor to acceptor atoms is low. text/html 42 salt forms of tyramine: structural comparison and the occurrence of hydrate formation text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science research papers 453 464 http://scripts.iucr.org/cgi-bin/paper?gp9038 Tables 2 and 3 in the paper by Tumanov et al. [(2010), Acta Cryst. B66, 458–471] are corrected. Copyright (c) 2012 International Union of Crystallography urn:issn:0108-7681 Tumanov, N.A. Boldyreva, E.V. Kolesov, B.A. Kurnosov, A.V. Quesada Cabrera, R. 2012-07-17 doi:10.1107/S010876811203193X International Union of Crystallography Corrigendum to the data published in the article by Tumanov et al. [(2010), Acta Cryst. B66, 458–471]. EN polymorphism amino acids pressure phase transitions Tables 2 and 3 in the paper by Tumanov et al. [(2010), Acta Cryst. B66, 458–471] are corrected. text/html Pressure-induced phase transitions in l-alanine, revisited. Corrigendum text 4 68 2012-07-17 Copyright (c) 2012 International Union of Crystallography Acta Crystallographica Section B: Structural Science addenda and errata 465 465