Acta Crystallographica Section C

Crystal Structure Communications

Polymorphism special issue (December 2011)

[Cover illustration]
Cover illustration: Differences in stacking for polymorphs of aspirin viewed down the b axis [Chan, Welberry, Heerdegen and Goossens (2010). Acta Cryst. B66, 696-707].


thumbnail of article figure
Acta Cryst. (2011). C67, e15    [doi:10.1107/S0108270111046968]

Virtual issue on polymorphism

A. Linden

Acta Crystallographica Section C is pleased to announce the publication of its first virtual issue. The issue is dedicated to the subject of polymorphism and includes papers relating to this topic published in Section C between January 2010 and November 2011.

polymorphism articles

thumbnail of article figure
Acta Cryst. (2010). C66, m44-m47    [doi:10.1107/S010827011000096X]

Two polymorphs of a lead(II) complex with 8-hydroxy-2-methylquinoline and thiocyanate

G. Mohammadnezhad, M. M. Amini and V. Langer

Two distinct polymorphs of bis([mu]2-methylquinolin-8-olato)-[kappa]3N,O:O;[kappa]3O:N,O-bis[(isothiocyanato-[kappa]N)lead(II)], [Pb2(C10H8NO)2(NCS)2], (I), forming dinuclear complexes from a methanolic solution containing lead(II) nitrate, 2-methylquinolin-8-ol (M-Hq) and KSCN, crystallized concomitantly as colourless prisms [form (Ia)] and long thin colourless needles [form (Ib)]. In both cases, the complexes lie across a centre of inversion. The polymorphs differ substantially in their conformation and in their interactions, viz. Pb...S and [pi]-[pi] for form (Ia) and Pb...S, Pb...[pi] and C-H...[pi] for form (Ib).

thumbnail of article figure
Acta Cryst. (2010). C66, o93-o96    [doi:10.1107/S0108270110001952]

Two concomitant polymorphs of N,N'-bis[4-(diethylamino)phenyl]terephthaldiamide

P. Kus, J. Borek and P. G. Jones

The title compound, C28H34N4O2, crystallizes simultaneously as a monoclinic, (Im), and a (twinned) triclinic polymorph, (It), from d6-dimethyl sulfoxide. Polymorph (It) (P\overline{1}, Z = 1) displays the standard `ladder' packing for this group of compounds, with neighbouring inversion-symmetric molecules related by translation and connected by hydrogen bonds of the form N-H...O=C. Polymorph (Im) (Cc, Z = 4) has no imposed symmetry; there are three independent hydrogen bonds, one classical N-H...O=C and a bifurcated system with N-H...O=C augmented by a short C-H...O=C interaction. Each molecule is thereby linked to four neighbouring molecules, two lower and two higher, so that a crosslinked three-dimensional pattern is formed rather than the standard ladder.

thumbnail of article figure
Acta Cryst. (2010). C66, m55-m57    [doi:10.1107/S0108270110001861]

Two polymorphs of chlorido(cyclohexyldiphenylphosphine)gold(I)

I. A. Guzei, I. Arachchige and S. A. Ivanov

The title compound, [AuCl(C18H21P)], a monomeric two-coordinate gold(I) complex, has been characterized at 100 K as two distinct monoclinic polymorphs, one from a single crystal, (Is), and one from a pseudo-merohedrally twinned crystal, (It). The molecular structures in the two monoclinic [P21/n for (Is) and P21/c for (It)] polymorphs are similar; however, the packing arrangements in the two lattices differ considerably. The structure of (It) is pseudo-merohedrally twinned by a twofold rotation about the a* axis.

thumbnail of article figure
Acta Cryst. (2010). C66, o114-o118    [doi:10.1107/S010827011000363X]

Two solid phases of pyrimidin-1-ium hydrogen chloranilate monohydrate determined at 225 and 120 K

K. Gotoh, T. Asaji and H. Ishida

The crystal structures of two solid phases of the title compound, C4H5N2+·C6HCl2O4-·H2O, have been determined at 225 and 120 K. In the high-temperature phase, stable above 198 K, the transition temperature of which has been determined by 35Cl nuclear quadrupole resonance and differential thermal analysis measurements, the three components are held together by O-H...O, N...H...O, C-H...O and C-H...Cl hydrogen bonds, forming a centrosymmetric 2+2+2 aggregate. In the N...H...O hydrogen bond formed between the pyrimidin-1-ium cation and the water molecule, the H atom is disordered over two positions, resulting in two states, viz. pyrimidin-1-ium-water and pyrimidine-oxonium. In the low-temperature phase, the title compound crystallizes in the same monoclinic space group and has a similar molecular packing, but the 2+2+2 aggregate loses the centrosymmetry, resulting in a doubling of the unit cell and two crystallographically independent molecules for each component in the asymmetric unit. The H atom in one N...H...O hydrogen bond between the pyrimidin-1-ium cation and the water molecule is disordered, while the H atom in the other hydrogen bond is found to be ordered at the N-atom site with a long N-H distance [1.10 (3) Å].

thumbnail of article figure
Acta Cryst. (2010). C66, o128-o132    [doi:10.1107/S010827011000541X]

p-Phenylenediamine and its dihydrate: two-dimensional isomorphism and mechanism of the dehydration process, and N-H...N and N-H...[pi] interactions

A. Czapik, H. Konowalska and M. Gdaniec

p-Phenylenediamine can be obtained as the dihydrate, C6H8N2·2H2O, (I), and in its anhydrous form, C6H8N2, (II). The asymmetric unit of (I) contains one half of the p-phenylenediamine molecule lying about an inversion centre and two halves of water molecules, one lying on a mirror plane and the other lying across a mirror plane. In (II), the asymmetric unit consists of one molecule in a general position and two half molecules located around inversion centres. In both structures, the p-phenylenediamine molecules are arranged in layers stabilized by N-H...[pi] interactions. The diamine layers in (I) are isostructural with half of the layers in (II). On dehydration, crystals of (I) transform to (II). Comparison of their crystal structures suggests the most plausible mechanism of the transformation process which requires, in addition to translational motion of the diamine molecules, in-plane rotation of every fourth p-phenylenediamine molecule by ca 60°. A search of the Cambridge Structural Database shows that the formation of hydrates by aromatic amines should be considered exceptional.

thumbnail of article figure
Acta Cryst. (2010). C66, o176-o178    [doi:10.1107/S0108270110004634]

The 293 K structure of tetradehydrohaliclonacyclamine A

I. W. Mudianta, M. J. Garson and P. V. Bernhardt

The polycyclic title compound {systematic name: (1S,16S,17S,31S)-3,20-diazatetracyclo[15.15.01,17.13,31.116,20]tetratriaconta-6,8,23,25-tetraene}, C32H52N2, has recently been isolated and characterized structurally, in solution by NMR spectroscopy and in the solid state by X-ray crystallography. At 130 K the structure is monoclinic (P21, Z = 4) and comprises two molecules in the asymmetric unit with distinctly different conformations in the twelve-C-atom bridging chains. We report that, at 250 K, a phase change from monoclinic to orthorhombic (P22121, Z = 4) occurs. The higher-temperature phase is structurally characterized herein at 293 K. The two different conformers resolved in the monoclinic low-temperature form merge to give a single disordered molecule in the asymmetric unit of the high-temperature phase.

thumbnail of article figure
Acta Cryst. (2010). C66, o198-o201    [doi:10.1107/S0108270110008474]

A new polymorph of benzene-1,2-diamine: isomorphism with 2-aminophenol and two-dimensional isostructurality of polymorphs

A. Czapik and M. Gdaniec

A new crystalline form of benzene-1,2-diamine, C6H8N2, crystallizing in the space group Pbca, has been identified during screening for cocrystals. The crystals are constructed from molecular bilayers parallel to (001) that have the polar amino groups directed to the inside and the aromatic groups, showing a herringbone arrangement, directed to the outside. The known monoclinic form and the new orthorhombic polymorph exhibit two-dimensional isostructurality as the crystals consist of nearly identical bilayers. In the monoclinic form, neighbouring bilayers are generated by a unit translation along the a axis, whereas in the orthorhombic form they are generated by a c-glide. Moreover, the new form of benzene-1,2-diamine is essentially isomorphous with the only known form of 2-aminophenol.

thumbnail of article figure
Acta Cryst. (2010). C66, i45-i49    [doi:10.1107/S0108270110010425]

A new modification of thallium chromate related to the [beta]-K2SO4 family

J. Fábry, M. Dusek, K. Fejfarová, R. Krupková and P. Vanek

The title structure is a new modification of Tl2CrO4. There are four independent Tl+ cations and two [CrO4]2- anions in the structure. It is closely related to the already known modification, which belongs to the [beta]-K2SO4 family with two independent cations and one anion. In both modifications, the cations and anions are situated on crystallographic mirror planes. The volume of the asymmetric unit of the title structure is ~0.4% smaller than that of the known modification belonging to the [beta]-K2SO4 family. The other difference between the two modifications is seen in the environment of the cations. In the title structure, none of the Tl+ cations is underbonded, in contrast with the modification isostructural with [beta]-K2SO4. In the [beta]-K2SO4 family with simple cations, underbonding of one of the constituent cations is typical. The dependence of the unit-cell parameters on temperature does not indicate a phase transition in the interval 90-300 K.

thumbnail of article figure
Acta Cryst. (2010). C66, i58-i60    [doi:10.1107/S0108270110014034]

Monoclinic Cu2Se3Sn

L. D. Gulay, M. Daszkiewicz, T. A. Ostapyuk, O. S. Klymovych and O. F. Zmiy

A previously unknown modification of dicopper(I) triselenostannate(IV), Cu2Se3Sn, has been obtained from the Cu2Se-SnSe2 quasi-binary system and investigated using X-ray single-crystal diffraction. The Se atoms are stacked in a closest-packed arrangement with the layers in the sequence ABC. The Cu atoms occupy one-third of the tetrahedral interstices, whereas the Sn atoms are located in one-sixth of the tetrahedral interstices. All the atoms occupy general positions. The structure possesses pseudo-inversion symmetry. The Cu2Se3Sn structure investigated in this paper (96 atoms per unit cell, ordered distribution of Cu and Sn over 12 cation positions) is a superstructure of the reported cubic (eight atoms per unit cell, random distribution of Cu and Sn over one cation position) and monoclinic (24 atoms per unit cell, ordered distribution of Cu and Sn over three cation positions) modifications.

thumbnail of article figure
Acta Cryst. (2010). C66, m137-m140    [doi:10.1107/S010827011001437X]

A new polymorph of dichloridotriphenylantimony

D. J. MacDonald, M. C. Jennings and K. E. Preuss

In a new polymorphic form of dichloridotriphenylantimony, [Sb(C6H5)3Cl2], there are two crystallographically unique molecules in the asymmetric unit and it has been determined that this polymorph is one of two kinetically favoured phases of pure dichloridotriphenylantimony, both of which have Z' > 1. A third polymorph, corresponding to (C6H5)3SbCl1.8F0.2, is also known and has Z' = 2. By contrast, the thermodynamically preferred polymorph of pure (C6H5)3SbCl2 has Z' = 1. A brief comparison of the known polymorphic forms of dichloridotriphenylantimony is presented.

thumbnail of article figure
Acta Cryst. (2010). C66, o241-o244    [doi:10.1107/S0108270110010280]

Hydrogen-bonded supramolecular networks of N,N'-bis(4-pyridylmethyl)oxalamide and 4,4'-{[oxalylbis(azanediyl)]dimethylene}dipyridinium dinitrate

G.-H. Lee

The molecule of N,N'-bis(4-pyridylmethyl)oxalamide, C14H14N4O2, (I) or 4py-ox, has an inversion center in the middle of the oxalamide group. Adjacent molecules are then linked through intermolecular N-H...N and C-H...O hydrogen bonds, forming an extended supramolecular network. 4,4'-{[Oxalylbis(azanediyl)]dimethylene}dipyridinium dinitrate, C14H16N4O22+·2NO3-, (II), contains a diprotonated 4py-ox cation and two nitrate counter-anions. Each nitrate ion is hydrogen bonded to four 4py-ox cations via intermolecular N-H...O and C-H...O interactions. Adjacent 4py-ox cations are linked through weak C-H...O hydrogen bonding between an [alpha]-pyridinium C atom and an oxalamide O atom, forming a two-dimensional extended supramolecular network.

thumbnail of article figure
Acta Cryst. (2010). C66, o260-o264    [doi:10.1107/S0108270110014393]

A third polymorph of 4-(2,6-difluorophenyl)-1,2,3,5-dithiadiazolyl

E. M. Fatila, M. C. Jennings, J. Goodreid and K. E. Preuss

The crystal structure of a third polymorphic form of the known 4-(2,6-difluorophenyl)-1,2,3,5-dithiadiazolyl radical, C7H3F2N2S2, is reported. This new polymorph represents a unique crystal-packing motif never before observed for 1,2,3,5-dithiadiazolyl (DTDA) radicals. In the two known polymorphic forms of the title compound, all of the molecules form cis-cofacial dimers, such that two molecules are [pi]-stacked with like atoms one on top of the other, a common arrangement for DTDA species. By contrast, the third polymorph, reported herein, contains two crystallographically unique molecules organized such that only 50% are dimerized, while the other 50% remain monomeric radicals. The dimerized molecules are arranged in the trans-antarafacial mode. This less common dimer motif for DTDA species is characterized by [pi]-[pi] interactions between the S atoms [S...S = 3.208 (1) Å at 110 K], such that the two molecules of the dimer are related by a centre of inversion. The most remarkable aspect of this third polymorph is that the DTDA dimers are co-packed with monomers. The monomeric radicals are arranged in one-dimensional chains directed by close lateral intermolecular contacts between the two S atoms of one DTDA heterocycle and an N atom of a neighbouring coplanar DTDA heterocycle [S...N = 2.857 (2) and 3.147 (2) Å at 110 K].

thumbnail of article figure
Acta Cryst. (2010). C66, i61-i63    [doi:10.1107/S0108270110016707]


W. T. A. Harrison

In poly[[diaquaoxido[[mu]3-trioxidoselenato(2-)]vanadium(IV)] hemihydrate], {[VO(SeO3)(H2O)2]·0.5H2O}n, the octahedral V(H2O)2O4 and pyramidal SeO3 building units are linked by V-O-Se bonds to generate ladder-like chains propagating along the [010] direction. A network of O-H...O hydrogen bonds helps to consolidate the structure. The O atom of the uncoordinated water molecule lies on a crystallographic twofold axis. The title compound has a similar structure to those of the reported phases [VO(OH)(H2O)(SeO3)]4·2H2O and VO(H2O)2(HPO4)·2H2O.

thumbnail of article figure
Acta Cryst. (2010). C66, i64-i66    [doi:10.1107/S0108270110017403]


W. T. A. Harrison

In the title compound, trizinc(II) diarsenite or trizinc(II) bis[trioxidoarsenate(III)], the constituent polyhedra that make up the structure are very distorted ZnO4 tetrahedra and AsO3 trigonal pyramids. These species fuse together to generate a three-dimensional network containing unusual edge-sharing tetrahedra, with a Zn...Zn separation of 2.903 (3) Å. The structure also features eight-ring pseudo-channels occupied by the AsIII lone pairs of electrons. The title compound is a polymorph of the mineral reinerite, which also features edge-shared ZnO4 tetrahedra.

thumbnail of article figure
Acta Cryst. (2010). C66, m145-m148    [doi:10.1107/S0108270110015581]

Bis(hinokitiolato)copper(II): modification (III)

D. M. Ho

Bis(hinokitiolato)copper(II), Cu(hino)2, exhibits both antibacterial and antiviral properties, and has been previously shown to exist in two modifications. A third modification has now been confirmed, namely tetrakis([mu]2-3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)bis(3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)tricopper(II)-bis([mu]2-3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)bis[(3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olato)copper(II)] (1/1), [Cu(C10H11O2)2]3·[Cu(C10H11O2)2]2, where 3-isopropyl-7-oxocyclohepta-1,3,5-trien-1-olate is the systematic name for the hinokitiolate anion. This new modification is composed of discrete [cis-Cu(hino)2]2[trans-Cu(hino)2] trimers and [cis-Cu(hino)2]2 dimers. The Cu atoms are bridged by [mu]2-O atoms from the hinokitiolate ligands to give distorted square-pyramidal and distorted octahedral CuII coordination environments. Hence, the CuII environments are CuO5/CuO6/CuO5 for the trimer and CuO5/CuO5 for the dimer. Each trimer and dimer has crystallographically imposed inversion symmetry. The trimer has never been observed before, the dimer has been seen only once before, and the combination of the two together in the same lattice is unprecedented. The CuO5 cores exhibit four strong basal Cu-O bonds [1.915 (2)-1.931 (2) Å] and one weak apical Cu-O bond [2.652 (2)-2.658 (2) Å]. The CuO6 core exhibits four strong equatorial Cu-O bonds [1.922 (2)-1.929 (2) Å] and two very weak axial Cu-O bonds [2.911 (3) Å]. The bite angles for the chelating hinokitiolate ligands range from 83.13 (11) to 83.90 (10)°.

thumbnail of article figure
Acta Cryst. (2010). C66, o270-o273    [doi:10.1107/S0108270110015428]

Polymorphs of DABCO monohydrate as structural analogues of NaCl

B. Wicher and M. Gdaniec

A new crystalline form of 1,4-diazabicyclo[2.2.2]octane (DABCO) monohydrate, C6H12N2·H2O, crystallizing in the space group P31, has been identified during screening for cocrystals. There are three DABCO and three water molecules in the asymmetric unit, with two DABCO molecules exhibiting disorder over two positions related by rotation around the N...N axis. As in the monoclinic C2/c (Z' = 2) polymorph, the molecular components are connected via O-H...N hydrogen bonds into a polymeric structure that consists of linear O-H...N(CH2CH2)3N...H-O segments, which are approximately mutually perpendicular. The two polymorphic forms of DABCO monohydrate can be considered as structural analogues of NaCl, with the nearly globular DABCO molecules showing distorted cubic closest packing and all octahedral interstices occupied by water molecules.

thumbnail of article figure
Acta Cryst. (2010). C66, o279-o283    [doi:10.1107/S0108270110015519]

Two new structures in the glycine-oxalic acid system

N. A. Tumanov, E. V. Boldyreva and N. E. Shikina

Glycinium semi-oxalate-II, C2H6NO2+·C2HO4-, (A), and diglycinium oxalate methanol disolvate, 2C2H6NO2+·C2O42-·2CH3OH, (B), are new examples in the glycine-oxalic acid family. (A) is a new polymorph of the known glycinium semi-oxalate salt, (C). Compounds (A) and (C) have a similar packing of the semi-oxalate monoanions with respect to the glycinium cations, but in (A) the two glycinium cations and the two semi-oxalate anions in the asymmetric unit are non-equivalent, and the binding of the glycinium cations to each other is radically different. Based on this difference, one can expect that, although the two forms grow concomitantly from the same batch, a transformation between (A) and (C) in the solid state should be difficult. In (B), two glycinium cations and an oxalate anion, which sits across a centre of inversion, are linked via strong short O-H...O hydrogen bonds to form the main structural fragment, similar to that in diglycinium oxalate, (D). Methanol solvent molecules are embedded between the glycinium cations of neighbouring fragments. These fragments form a three-dimensional network via N-H...O hydrogen bonds. Salts (B) and (D) can be obtained from the same solution by, respectively, slow or rapid antisolvent crystallization.

thumbnail of article figure
Acta Cryst. (2010). C66, o317-o320    [doi:10.1107/S0108270110019384]

Two polymorphs of safinamide, a selective and reversible inhibitor of monoamine oxidase B

K. Ravikumar and B. Sridhar

Two polymorphs of safinamide {systematic name: (2S)-2-[4-(3-fluorobenzyloxy)benzylamino]propionamide}, C17H19FN2O2, a potent selective and reversible monoamine oxidase B (MAO-B) inhibitor, are described. Both forms are orthorhombic and regarded as conformational polymorphs due to the differences in the orientation of the 3-fluorobenzyloxy and propanamide groups. Both structures pack with layers in the ac plane. In polymorph (I), the layers have discrete wide and narrow regions which are complementary when located next to adjacent layers. In polymorph (II), the layer has long flanges protruding from each side, which interdigitate when packed with the adjacent layers. N-H...O hydrogen bonds are present in both structures, whereas N-H...F hydrogen bonding is seen in polymorph (I), while N-H...N hydrogen bonding is seen in polymorph (II).

thumbnail of article figure
Acta Cryst. (2010). C66, o341-o344    [doi:10.1107/S0108270110019190]

Ezetimibe anhydrate, determined from laboratory powder diffraction data

J. Brüning, E. Alig and M. U. Schmidt

Ezetimibe {systematic name: (3R,4S)-1-(4-fluorophenyl)-3-[(3S)-3-(4-fluorophenyl)-3-hydroxypropyl]-4-(4-hydroxyphenyl)azetidin-2-one}, C24H21F2NO3, is used to lower cholesterol levels by inhibiting cholesterol resorption in the human intestine. The crystal structure of ezetimibe anhydrate was solved from laboratory powder diffraction data by means of real-space methods using the program DASH [David et al. (2006). J. Appl. Cryst. 39, 910-915]. Subsequent Rietveld refinement with TOPAS Academic [Coelho (2007). TOPAS Academic User Manual. Version 4.1. Coelho Software, Brisbane, Australia] led to a final Rwp value of 8.19% at 1.75 Å resolution. The compound crystallizes in the space group P212121 with one molecule in the asymmetric unit. The molecules are closely packed and two intermolecular hydrogen bonds form an extended hydrogen-bond architecture.

thumbnail of article figure
Acta Cryst. (2010). C66, o364-o368    [doi:10.1107/S0108270110019827]

Structural comparison of three N-(4-halogenophenyl)-N'-[1-(2-pyridyl)ethylidene]hydrazine hydrochlorides

J. Heilmann-Brohl, M. Wagner, H.-W. Lerner and M. Bolte

2-{1-[(4-Chloroanilino)methylidene]ethyl}pyridinium chloride methanol solvate, C13H13ClN3+·Cl-·CH3OH, (I), crystallizes as discrete cations and anions, with one molecule of methanol as solvent in the asymmetric unit. The N-C-C-N torsion angle in the cation indicates a cis conformation. The cations are located parallel to the (\overline{2}02) plane and are connected through hydrogen bonds by a methanol solvent molecule and a chloride anion, forming zigzag chains in the direction of the b axis. The crystal structure of 2-{1-[(4-fluoroanilino)methylidene]ethyl}pyridinium chloride, C13H13FN3+·Cl-, (II), contains just one anion and one cation in the asymmetric unit but no solvent. In contrast with (I), the N-C-C-N torsion angle in the cation corresponds with a trans conformation. The cations are located parallel to the (100) plane and are connected by hydrogen bonds to the chloride anions, forming zigzag chains in the direction of the b axis. In addition, the crystal packing is stabilized by weak [pi]-[pi] interactions between the pyridinium and benzene rings. The crystal of (II) is a nonmerohedral monoclinic twin which emulates an orthorhombic diffraction pattern. Twinning occurs via a twofold rotation about the c axis and the fractional contribution of the minor twin component refined to 0.324 (3). 2-{1-[(4-Fluoroanilino)methylidene]ethyl}pyridinium chloride methanol disolvate, C13H13FN3+·Cl-·2CH3OH, (III), is a pseudopolymorph of (II). It crystallizes with two anions, two cations and four molecules of methanol in the asymmetric unit. Two symmetry-equivalent cations are connected by hydrogen bonds to a chloride anion and a methanol solvent molecule, forming a centrosymmetric dimer. A further methanol molecule is hydrogen bonded to each chloride anion. These aggregates are connected by C-H...O contacts to form infinite chains. It is remarkable that the geometric structures of two compounds having two different formula units in their asymmetric units are essentially the same.

thumbnail of article figure
Acta Cryst. (2010). C66, o441-o445    [doi:10.1107/S0108270110029021]

Green chemistry synthesis: 2-amino-3-[(E)-(2-pyridyl)methylideneamino]but-2-enedinitrile monohydrate and 5-cyano-2-(2-pyridyl)-1-(2-pyridylmethyl)-1H-imidazole-4-carboxamide

M. Altaf and H. Stoeckli-Evans

The title compounds, C10H9N5O·H2O (L1·H2O) and C16H12N6O (L2), were synthesized by solvent-free aldol condensation at room temperature. L1, prepared by grinding picolinaldehyde with 2,3-diamino-3-isocyanoacrylonitrile in a 1:1 molar ratio, crystallized as a monohydrate. L2 was prepared by grinding picolinaldehyde with 2,3-diamino-3-isocyanoacrylonitrile in a 2:1 molar ratio. By varying the conditions of crystallization it was possible to obtain two polymorphs, viz. L2-I and L2-II; both crystallized in the monoclinic space group P21/c. They differ in the orientation of one pyridine ring with respect to the plane of the imidazole ring. In L2-I, this ring is oriented towards and above the imidazole ring, while in L2-II it is rotated away from and below the imidazole ring. In all three molecules, there is a short intramolecular N-H...N contact inherent to the planarity of the systems. In L1·H2O, this involves an amino H atom and the C=N N atom, while in L2 it involves an amino H atom and an imidazole N atom. In the crystal structure of L1·H2O, there are N-H...O and O-H...O intermolecular hydrogen bonds which link the molecules to form two-dimensional networks which stack along [001]. These networks are further linked via intermolecular N-H...N(cyano) hydrogen bonds to form an extended three-dimensional network. In the crystal structure of L2-I, symmetry-related molecules are linked via N-H...N hydrogen bonds, leading to the formation of dimers centred about inversion centres. These dimers are further linked via N-H...O hydrogen bonds involving the amide group, also centred about inversion centres, to form a one-dimensional arrangement propagating in [100]. In the crystal structure of L2-II, the presence of intermolecular N-H...O hydrogen bonds involving the amide group results in the formation of dimers centred about inversion centres. These are linked via N-H...N hydrogen bonds involving the second amide H atom and the cyano N atom, to form two-dimensional networks in the bc plane. In L2-I and L2-II, C-H...[pi] and [pi]-[pi] interactions are also present.

thumbnail of article figure
Acta Cryst. (2010). C66, o463-o465    [doi:10.1107/S0108270110028544]

A monohydrate pseudopolymorph of 3,4-dihydroxybenzophenone and the role of water in the crystal assembly of benzophenones

I. M. R. Landre, T. E. Souza, R. S. Corrêa, F. T. Martins and A. C. Doriguetto

During a polymorphism screening of hydroxybenzophenone derivatives, a monohydrate pseudopolymorph of (3,4-dihydroxyphenyl)(phenyl)methanone, C13H10O3·H2O, (I), was obtained. Structural relationships and the role of water in crystal assembly were established on the basis of the known anhydrous form [Cox, Kechagias & Kelly (2008). Acta Cryst. B64, 206-216]. The crystal packing of (I) is stabilized by classical intermolecular O-H...O hydrogen bonds, generating a three-dimensional network.

thumbnail of article figure
Acta Cryst. (2010). C66, o479-o483    [doi:10.1107/S0108270110032014]

Powder X-ray studies of meso-hexamethyl propylene amine oxime (meso-HMPAO) in two different phases

M. Al-Ktaifani and M. Rukiah

Two different forms of meso-3,3'-[2,2-dimethylpropane-1,3-diylbis(azanediyl)]dibutan-2-one dioxime, commonly called meso-hexamethyl propylene amine oxime (HMPAO), C13H28N4O2, designated [alpha] and [beta], were isolated by fractional crystallization and their crystal structures were determined by powder X-ray diffraction using the direct-space method with the parallel tempering algorithm. The [alpha] form was first crystallized from acetonitrile solution, while the [beta] form was obtained by recrystallization of the [alpha] phase from diethyl ether. The [alpha] form crystallizes in the triclinic system (space group P\overline{1}), with one molecule in the asymmetric unit, while the crystal of the [beta] form is monoclinic (space group P21/n), with one molecule in the asymmetric unit. In both phases, the molecules have similar conformations and RS/EE geometric isomerism. The crystal packing of the two phases is dominated by intermolecular hydrogen-bonding interactions between the two O-H oxime groups of an individual molecule and the amine N atoms of two different adjacent molecules, which lead to segregation of extended poly(meso-HMPAO) one-dimensional chains along the c direction. The structures of the two phases are primarily different due to the different orientations of the molecules in the chains.

thumbnail of article figure
Acta Cryst. (2010). C66, m303-m306    [doi:10.1107/S0108270110037017]

A low-temperature phase of bis(tetrabutylammonium) octa-[mu]3-chlorido-hexachlorido-octahedro-hexatungstate

D. H. Johnston, C. M. Brown, A. S. Yu and J. C. Gallucci

The title compound, (C16H36N)2[W6Cl14], undergoes a reversible phase transition at 268 (1) K. The structure at 150 and 200 K has monoclinic (P21/c) symmetry. Both crystallographically independent tungsten chloride cluster anions sit on crystallographic inversion centers [symmetry codes: (-x, -y + 1, -z) and (-x + 1, -y + 2, -z)]. Two previous studies at room temperature describe the structure in the space group P21/n with a unit-cell volume approximately half the size of the low-temperature unit cell [Zietlow, Schaefer et al. (1986). Inorg. Chem. 25, 2195-2198; Venkataraman et al. (1999). Inorg. Chem. 38, 828-830]. The unit cells of the room- and low-temperature polymorphs are closely related. The hydrocarbon chain of one of the tetrabutylammonium cations is disordered at both 150 and 200 K.

thumbnail of article figure
Acta Cryst. (2010). C66, o508-o512    [doi:10.1107/S0108270110034657]

Two three-dimensional networks in two polymorphs of biphenyl-4,4'-diaminium bis(3-carboxy-4-hydroxybenzenesulfonate) dihydrate

W. Yin, X. Huang, X. Xu and X. Meng

Two polymorphs of biphenyl-4,4'-diaminium bis(3-carboxy-4-hydroxybenzenesulfonate) dihydrate, C12H14N22+·2C7H5O6S-·2H2O, have been obtained and crystallographically characterized. Polymorph (I) crystallizes in the space group P21/c with Z' = 2 and polymorph (II) in the space group P\overline{1} with Z' = 0.5. The benzidinium cation in (II) is located on a crystallographic inversion centre. In both (I) and (II), the sulfonic acid H atoms are transferred to the benzidine N atoms, forming dihydrated 1:2 molecular adducts (base-acid). In the crystal packings of (I) and (II), the component ions are linked into three-dimensional networks by combinations of X-H...O (X = O, N and C) hydrogen bonds. In addition, [pi]-[pi] interactions are observed in (I) between inversion-related benzene rings [centroid-centroid distances = 3.632 (2) and 3.627 (2) Å]. In order to simplify the complex three-dimensional networks in (I) and (II), we also give their rationalized topological analyses.

thumbnail of article figure
Acta Cryst. (2010). C66, m330-m335    [doi:10.1107/S0108270110041466]

Twinned low-temperature structures of tris(ethylenediamine)zinc(II) sulfate and tris(ethylenediamine)copper(II) sulfate

M. Lutz

Tris(ethylenediamine)zinc(II) sulfate, [Zn(C2H8N2)3]SO4, (I), undergoes a reversible solid-solid phase transition during cooling, accompanied by a lowering of the symmetry from high-trigonal P\overline{3}1c to low-trigonal P\overline{3} and by merohedral twinning. The molecular symmetries of the cation and anion change from 32 (D3) to 3 (C3). This lower symmetry allows an ordered sulfate anion and generates in the complex cation two independent N atoms with significantly different geometries. The twinning is the same as in the corresponding Ni complex [Jameson et al. (1982). Acta Cryst. B38, 3016-3020]. The low-temperature phase of tris(ethylenediamine)copper(II) sulfate, [Cu(C2H8N2)3]SO4, (II), has only triclinic symmetry and the unit-cell volume is doubled with respect to the room-temperature structure in P\overline{3}1c. (II) was refined as a nonmerohedral twin with five twin domains. The asymmetric unit contains two independent formula units, and all cations and anions are located on general positions with 1 (C1) symmetry. Both molecules of the Cu complex are in elongated octahedral geometries because of the Jahn-Teller effect. This is in contrast to an earlier publication, which describes the complex as a compressed octahedron [Bertini et al. (1979). J. Chem. Soc. Dalton Trans. pp. 1409-1414].

thumbnail of article figure
Acta Cryst. (2010). C66, i99-i102    [doi:10.1107/S0108270110046299]

The structural phase transition in SrV6O11

Y. Hata, Y. Kanke and E. Kita

Single-crystal X-ray diffraction and specific heat studies establish that strontium hexavanadium undecaoxide, SrV6O11, undergoes a P63/mmc to inversion twinned P63mc structural transition as the temperature is lowered through 322 K. The P63/mmc and P63mc structures have been determined at 353 K and at room temperature, respectively. For the room-temperature structure, seven of the ten unique atoms lie on special positions, and for the 353 K structure all of the seven unique atoms sit on special positions. The P63/mmc to P63mc structural phase transition, accompanied by a magnetic transition, is a common characteristic of AV6O11 compounds, independent of the identity of the A cations.

thumbnail of article figure
Acta Cryst. (2010). C66, o593-o595    [doi:10.1107/S0108270110045099]

Polymorphism in 2-(4-hydroxy-2,6-dimethylanilino)-5,6-dihydro-4H-1,3-thiazin-3-ium chloride

J. Gutierrez, R. Eisenberg, G. Herrensmith, T. Tobin, T. Li and S. Long

Details of the structures of two conformational polymorphs of the title compound, C12H17N2OS+·Cl-, are reported. In form (I) (space group P\overline{1}), the two N-H groups of the cation are in a trans conformation, while in form (II) (space group P21/c), they are in a cis arrangement. This results in different packing and hydrogen-bond arrangements in the two forms, both of which have extended chains lying along the a direction. In form (I), these chains are composed of centrosymmetric R42(18) (N-H...Cl and O-H...Cl) hydrogen-bonded rings and R22(18) (N-H...O) hydrogen-bonded rings. In form (II), the chains are formed by centrosymmetric R42(18) (N-H...Cl and O-H...Cl) hydrogen-bonded rings and by R42(12) (N-H...Cl) hydrogen-bonded rings.

thumbnail of article figure
Acta Cryst. (2010). C66, o609-o613    [doi:10.1107/S010827011004672X]

Anhydrous 1:1 proton-transfer compounds of isonipecotamide with picric acid and 3,5-dinitrosalicylic acid: 4-carbamoylpiperidinium 2,4,6-trinitrophenolate and two polymorphs of 4-carbamoylpiperidinium 2-carboxy-4,6-dinitrophenolate

G. Smith and U. D. Wermuth

The structures of the anhydrous 1:1 proton-transfer compounds of isonipecotamide (piperidine-4-carboxamide) with picric acid and 3,5-dinitrosalicylic acid, namely 4-carbamoylpiperidinium 2,4,6-trinitrophenolate, C6H13N2O+·C6H2N3O7-, (I), and 4-carbamoylpiperidinium 2-carboxy-4,6-dinitrophenolate [two forms of which were found, the monoclinic [alpha]-polymorph, (II), and the triclinic [beta]-polymorph, (III)], C6H13N2O+·C7H3N2O7-, have been determined at 200 K. All three compounds form hydrogen-bonded structures, viz. one-dimensional in (II), two-dimensional in (I) and three-dimensional in (III). In (I), the cations form centrosymmetric cyclic head-to-tail hydrogen-bonded homodimers [graph set R22(14)] through lateral duplex piperidinium-amide N-H...O interactions. These dimers are extended into a two-dimensional network structure through further interactions with phenolate and nitro O-atom acceptors, including a direct symmetric piperidinium-phenol/nitro N-H...O,O cation-anion association [graph set R12(6)]. The monoclinic polymorph, (II), has a similar R12(6) cation-anion hydrogen-bonding interaction to (I) but with an additional conjoint symmetrical R12(4) interaction as well as head-to-tail piperidinium-amide N-H...O,O hydrogen bonds and amide-carboxyl N-H...O hydrogen bonds, giving a network structure which includes large R43(20) rings. The hydrogen bonding in the triclinic polymorph, (III), is markedly different from that of monoclinic (II). The asymmetric unit contains two independent cation-anion pairs which associate through cyclic piperidinium-carboxyl N-H...O,O' interactions [graph set R12(4)]. The cations also show the zigzag head-to-tail piperidinium-amide N-H...O hydrogen-bonded chain substructures found in (II), but in addition feature amide-nitro and amide-phenolate N-H...O associations. As well, there is a centrosymmetric double-amide N-H...Ocarboxyl bridged bis(cation-anion) ring system [graph set R42(8)] in the three-dimensional framework. The structures reported here demonstrate the utility of the isonipecotamide cation as a synthon with previously unrecognized potential for structure assembly applications. Furthermore, the structures of the two polymorphic 3,5-dinitrosalicylic acid salts show an unusual dissimilarity in hydrogen-bonding characteristics, considering that both were obtained from identical solvent systems.

thumbnail of article figure
Acta Cryst. (2011). C67, o6-o9    [doi:10.1107/S0108270110046317]

Two new polymorphs of 2,6-diaminopyrimidin-4(3H)-one monohydrate

N. Suleiman Gwaram, H. Khaledi, H. Mohd Ali and M. M. Olmstead

The title compound, C4H6N4O·H2O, crystallized simultaneously as a triclinic and a monoclinic polymorph from an aqueous solution of 2,4-diaminopyrimidin-6-ol. Previously, an orthorhombic polymorph was isolated under the same experimental conditions. The molecular geometric parameters in the two present polymorphs and the previously reported orthorhombic polymorph are similar, but the structures differ in the details of their crystal packing. In the triclinic system, the diaminopyrimidinone molecules are connected to one another via N-H...O and N-H...N hydrogen bonding to form infinite chains in the [011] direction. The chains are further hydrogen bonded to the water molecules, resulting in a three-dimensional network. In the monoclinic system, the diaminopyrimidinone molecules are hydrogen bonded together into two-dimensional networks parallel to the bc plane. The water molecules link the planes to form a three-dimensional polymeric structure.

thumbnail of article figure
Acta Cryst. (2011). C67, o18-o25    [doi:10.1107/S0108270110046755]

Five pseudopolymorphs and a cocrystal of nitrofurantoin

M. Tutughamiarso, M. Bolte, G. Wagner and E. Egert

The antibiotic nitrofurantoin {systematic name: (E)-1-[(5-nitro-2-furyl)methylideneamino]imidazolidine-2,4-dione} is not only used for the treatment of urinary tract infections, but also illegally applied as an animal food additive. Since derivatives of 2,6-diaminopyridine might serve as artificial receptors for its recognition, we crystallized one potential drug-receptor complex, nitrofurantoin-2,6-diacetamidopyridine (1/1), C8H6N4O5·C9H11N3O2, (I·II). It is characterized by one N-H...N and two N-H...O hydrogen bonds and confirms a previous NMR study. During the crystallization screening, several new pseudopolymorphs of both components were obtained, namely a nitrofurantoin dimethyl sulfoxide monosolvate, C8H6N4O5·C2H6OS, (Ia), a nitrofurantoin dimethyl sulfoxide hemisolvate, C8H6N4O5·0.5C2H6OS, (Ib), two nitrofurantoin dimethylacetamide monosolvates, C8H6N4O5·C4H9NO, (Ic) and (Id), and a nitrofurantoin dimethylacetamide disolvate, C8H6N4O5·2C4H9NO, (Ie), as well as a 2,6-diacetamidopyridine dimethylformamide monosolvate, C9H11N3O2·C3H7NO, (IIa). Of these, (Ia), (Ic) and (Id) were formed during cocrystallization attempts with 1-(4-fluorophenyl)biguanide hydrochloride. Obviously nitrofurantoin prefers the higher-energy conformation in the crystal structures, which all exhibit N-H...O and C-H...O hydrogen-bond interactions. The latter are especially important for the crystal packing. 2,6-Diacetamidopyridine shows some conformational flexibility depending on the hydrogen-bond pattern.

thumbnail of article figure
Acta Cryst. (2011). C67, m111-m114    [doi:10.1107/S0108270111008353]

A dynamic disorder-linked reversible phase transition in a new chloroform solvate of cis-dichloridobis(triethylphosphane)platinum(II)

K. B. Dillon, J. A. K. Howard, P. K. Monks, M. R. Probert and H. J. Shepherd

The title compound, cis-dichloridobis(triethylphosphane)platinum(II) chloroform monosolvate, [PtCl2(C6H15P)2]·CHCl3, has been obtained from ligand scrambling in the cis-[PtCl2(Cyp2PCl)(PEt3)] (Cyp = cyclopentyl) system in CHCl3 solvent. Unlike the two previously reported unsolvated polymorphs, which are both monoclinic, the compound crystallizes in an orthorhombic setting. Furthermore, the system exhibits a reversible temperature-dependent structural phase transition, coupling a reduction in anisotropic displacement parameters and a reduction in crystallographic symmetry on cooling. The high-temperature phase adopts space group Pnma with the complex and solvent molecules sitting across a crystallographic mirror plane (Z' = 0.5). The low-temperature phase adopts the space group P212121 with Z' = 1.

thumbnail of article figure
Acta Cryst. (2011). C67, o131-o133    [doi:10.1107/S0108270111008742]

A new polymorph of 1,4-dibromo-2,5-dimethylbenzene: H...Br and Br...[pi] versus Br...Br interactions

P. G. Jones and P. Kus

A new polymorph, (Ib), of the title compound, C8H8Br2, crystallizes in the space group P21/n, the same as the known polymorph (Ia) but with Z = 2 (imposed inversion symmetry) rather than Z = 4. The molecular structures are closely similar because the molecule has no degrees of torsional freedom except for methyl groups, but the packing arrangements are completely different. Polymorph (Ia) is characterized by linked trapezia of Br...Br interactions, whereas polymorph (Ib) features H...Br and Br...[pi] interactions.

thumbnail of article figure
Acta Cryst. (2011). C67, o139-o142    [doi:10.1107/S0108270111009760]

L-Cysteinium semioxalate: a new monoclinic polymorph or a hydrate?

V. S. Minkov and E. V. Boldyreva

The title compound, C3H8NO2S+·C2HO4-, (I), crystallizes in the monoclinic C2 space group and is a new form (possibly a hydrate) of L-cysteinium semioxalate with a stoichiometric cation-anion ratio of 1:1. In contrast to the previously known orthorhombic form of L-cysteinium semioxalate, (I) has a layered structure resembling those of monoclinic L-cysteine, as well as of DL-cysteine and its oxalates. The conformations of the cysteinium cation and the oxalate anion in (I) differ substantially from those in the orthorhombic form. The structure of (I) has voids with a size sufficient to incorporate water molecules. The residual density, however, suggests that if water is in fact present in the voids, it is strongly disordered and its amount does not exceed 0.3 molecules per void. The difference in conformation of the cysteinium cations in (I) and in the orthorhombic form is similar to that in DL-cysteine under ambient conditions and in DL-cysteine under high pressure or at low temperature.

thumbnail of article figure
Acta Cryst. (2011). C67, i30-i32    [doi:10.1107/S0108270111012273]

Synthetic ferric sulfate trihydrate, Fe2(SO4)3·3H2O, a new ferric sulfate salt

W. Xu and J. B. Parise

Ferric sulfate trihydrate has been synthesized at 403 K under hydrothermal conditions. The structure consists of quadruple chains of [Fe2(SO4)3(H2O)3]^0_{\infty} parallel to [010]. Each quadruple chain is composed of equal proportions of FeO4(H2O)2 octahedra and FeO5(H2O) octahedra sharing corners with SO4 tetrahedra. The chains are joined to each other by hydrogen bonds. This compound is a new hydration state of Fe2(SO4)3·nH2O; minerals with n = 0, 5, 7.25-7.75, 9 and 11 are found in nature.

thumbnail of article figure
Acta Cryst. (2011). C67, m149-m153    [doi:10.1107/S0108270111013035]

Two polymorphs of tetraethylammonium [hydrogen tris(3,5-dimethylpyrazolyl)borato]di-[mu]2-sulfido-disulfido([eta]2-tetrasulfido)ditungsten(V) with Z' = 1 and 2

A. Beheshti, W. Clegg, N. Ebrahimi Filoori and L. Russo

Two polymorphs of the title compound, (C8H20N)[W2S4(S4)(C15H22BN6)], have been obtained unexpectedly by attempted recrystallization of a mixed-metal-sulfur cluster complex from different solvents. The dinuclear complex anion contains WV in two different coordination environments, one of them distorted octahedral with a tris(pyrazolyl)borate anion, a terminal sulfide and two bridging sulfide ligands, the other distorted square-pyramidal with a terminal sulfide, two bridging sulfide and a chelating tetrasulfide ligand. The three independent anions in the two polymorphs have essentially the same geometry. The central W2S2 ring is a slightly folded rhombus with acute angles at the S atoms, and the WS4 chelate ring is an envelope with one noncoordinating S atom as the flap. The second polymorph, with Z' = 2 and pseudo-inversion symmetry relating the anions of the asymmetric unit, also displays pseudo-translation features in its layer structure, and all examined crystals were found to be twinned, possibly as a consequence of this structural feature.

thumbnail of article figure
Acta Cryst. (2011). C67, o171-o174    [doi:10.1107/S0108270111010109]

Conformational polymorphism of (E,E)-N,N'-bis(4-nitrobenzylidene)benzene-1,4-diamine

A. Collas, M. Zeller and F. Blockhuys

Two polymorphs of (E,E)-N,N'-bis(4-nitrobenzylidene)benzene-1,4-diamine, C20H14N4O4, (I), have been identified. In each case, the molecule lies across a crystallographic inversion centre. The supramolecular structure of the first polymorph, (I-1), features stacking based on [pi]-[pi] interactions assisted by weak hydrogen bonds involving the nitro groups. The second polymorph, (I-2), displays a perpendicular arrangement of molecules linked via the nitro groups, combined with weak C-H...O hydrogen bonds. Both crystal structures are compared with that of the carbon analogue (E,E)-1,4-bis[2-(4-nitrophenyl)ethenyl]benzene, (II).

thumbnail of article figure
Acta Cryst. (2011). C67, o179-o187    [doi:10.1107/S0108270111013072]

Pseudopolymorphs of 2,6-diaminopyrimidin-4-one and 2-amino-6-methylpyrimidin-4-one: one or two tautomers present in the same crystal

V. Gerhardt, M. Tutughamiarso and M. Bolte

The derivatives of pyrimidin-4-one can adopt either a 1H- or a 3H-tautomeric form, which affects the hydrogen-bonding interactions in cocrystals with compounds containing complementary functional groups. In order to study their tautomeric preferences, we crystallized 2,6-diaminopyrimidin-4-one and 2-amino-6-methylpyrimidin-4-one. During various crystallization attempts, four structures of 2,6-diaminopyrimidin-4-one were obtained, namely solvent-free 2,6-diaminopyrimidin-4-one, C4H6N4O, (I), 2,6-diaminopyrimidin-4-one-dimethylformamide-water (3/4/1), C4H6N4O·1.33C3H7NO·0.33H2O, (Ia), 2,6-diaminopyrimidin-4-one dimethylacetamide monosolvate, C4H6N4O·C4H9NO, (Ib), and 2,6-diaminopyrimidin-4-one-N-methylpyrrolidin-2-one (3/2), C4H6N4O·1.5C5H9NO, (Ic). The 2,6-diaminopyrimidin-4-one molecules exist only as 3H-tautomers. They form ribbons characterized by R22(8) hydrogen-bonding interactions, which are further connected to form three-dimensional networks. An intermolecular N-H...N interaction between amine groups is observed only in (I). This might be the reason for the pyramidalization of the amine group. Crystallization experiments on 2-amino-6-methylpyrimidin-4-one yielded two isostructural pseudopolymorphs, namely 2-amino-6-methylpyrimidin-4(3H)-one-2-amino-6-methylpyrimidin-4(1H)-one-dimethylacetamide (1/1/1), C5H7N3O·C5H7N3O·C4H9NO, (IIa), and 2-amino-6-methylpyrimidin-4(3H)-one-2-amino-6-methylpyrimidin-4(1H)-one-N-methylpyrrolidin-2-one (1/1/1), C5H7N3O·C5H7N3O·C5H9NO, (IIb). In both structures, a 1:1 mixture of 1H- and 3H-tautomers is present, which are linked by three hydrogen bonds similar to a Watson-Crick C-G base pair.

thumbnail of article figure
Acta Cryst. (2011). C67, m173-m175    [doi:10.1107/S0108270111016507]

Poly[([mu]3-benzene-1,4-diacetato)[[mu]2-1,4-bis(1,2,4-triazol-1-yl)butane]cadmium(II)]: self assembly into a three-dimensional supramolecular framework based on [Cd([mu]3-benzene-1,4-diacetate)] double chains

J. Wang, J.-Q. Tao and X.-J. Xu

The title compound, [Cd(C10H8O4)(C8H12N6)]n, crystallizes with an asymmetric unit comprising a divalent CdII atom, a benzene-1,4-diacetate (PBEA2-) ligand and a complete 1,4-bis(1,2,4-triazol-1-yl)butane (BTB) ligand. [Cd(PBEA)]n double chains, arranged parallel to the c axis, are formed through an exo-tridentate binding mode of the PBEA2- ligands. These [Cd(PBEA)]n double chains are pillared by tethering BTB ligands, in which the BTB shows a trans-trans-trans conformation, to establish [Cd(PBEA)(BTB)]n two-dimensional coordination polymer (4,4)-layer slab patterns. The three-dimensional supramolecular architecture is formed by C-H...O hydrogen bonds and C-H...[pi] interactions.

thumbnail of article figure
Acta Cryst. (2011). C67, o195-o197    [doi:10.1107/S0108270111013163]

Two polymorphs of (2-carboxyethyl)(phenyl)phosphinic acid

Q.-S. Hu, X.-Z. Zhang, S.-F. Luo, Y.-H. Sun and Z.-Y. Du

Two polymorphs of (2-carboxyethyl)(phenyl)phosphinic acid, C9H11O4P, crystallize in the chiral P212121 space group with similar unit-cell parameters. They feature an essentially similar hydrogen-bonding motif but differ slightly in their detailed geometric parameters. For both polymorphs, the unequivocal location of the hydroxy H atoms together with the expected differences in the P-O bond lengths establish unequivocally that both forms contain the S isomer; the protonated phosphinic acid and carboxy O atoms serve as hydrogen-bond donors, while the second phosphinic acid O atom acts as a double hydrogen-bond acceptor and the remaining carboxy O atom is not involved in hydrogen bonding. Thus, an undulating two-dimensional supramolecular layer aggregate is formed based on an R43(20) ring unit. Such polymorphism derives from the rotation of the C-C single bonds between the two hydrogen-bond-involved carboxy and phosphinic acid moieties.

thumbnail of article figure
Acta Cryst. (2011). C67, o212-o218    [doi:10.1107/S0108270111017501]

1,5-Dianilinopentane-1,3,5-trione: a crystal structure containing two polymorphic domains

J. W. Bats, J. Brüning and M. U. Schmidt

Single crystals of the title compound, C17H16N2O3, were obtained by gas diffusion. The observed diffraction pattern is compatible with a superposition of reflections from two monoclinic unit cells with the space group C2/c. The two cells share the a and b axes but not the c axis. Both structures contain layers parallel to (001), with molecules connected by intermolecular N-H...O=C hydrogen bonds. The bonding between adjacent layers is weak. Layer displacements result in a crystal structure containing two closely related polymorphic domains. The structure of one polymorph can be derived from the structure of the other if subsequent layers are displaced by (a/4, b/4, 0) for odd-numbered layers and by (a/4, -b/4, 0) for even-numbered layers. Three different crystals were analysed and their observed diffraction patterns were similar, showing all three crystals to contain the polymorphic domain structure.

thumbnail of article figure
Acta Cryst. (2011). C67, i42-i44    [doi:10.1107/S0108270111022359]

A new rhombohedral modification of EuNi5In

I. Bigun, V. Smetana and Y. Kalychak

A rhombohedral modification of europium pentanickel indide, r-EuNi5In, crystallizes in the R\overline{3}m space group and adopts the UCu5In structure type. The structure is closely related to the hexagonal, h-EuNi5In, form (CeNi5Sn type). Both EuNi5In modifications are composed of CaCu5 (EuNi5)-, MgCu2 (InNi2)- and NiAs (EuNi)-type slabs in a 1:2:1 ratio. The atoms in the structure have high coordination numbers, viz. 20 and 18 for europium, 14 for indium, and 12 and 10 for nickel. The structure features a two-dimensional network of 2[infinity][Ni8] tetrahedral clusters arranged in the ab plane.

thumbnail of article figure
Acta Cryst. (2011). C67, o222-o225    [doi:10.1107/S0108270111019688]

1-(9H-Carbazol-4-yloxy)-3-{[2-(2-methoxyphenoxy)ethyl]amino}propan-2-ol hemihydrate: a carvedilol solvatomorph

F. Díaz, A. Benassi, M. Quintero, G. Polla, E. Freire and R. Baggio

In the title racemic hemihydrated solvatomorph of carvedilol (carv), C24H26N2O4·0.5H2O, the asymmetric unit contains two independent organic moieties and one water molecule. Within this 2(carv)·H2O unit, the molecular components are strongly linked by hydrogen bonds and the unit acts as the basic building block for the crystal structure. Interactions parallel to (10\overline{1}) generate hydrogen-bonded layers which are further linked by much weaker C-H...N/O interactions. The conformations of the organic molecules, as well as the hydrogen-bonding interactions connecting them, are compared with other related structures in the literature.

thumbnail of article figure
Acta Cryst. (2011). C67, o249-o254    [doi:10.1107/S0108270111020816]

Polysulfonylamines. CXCI. The `almost' polymorphs rac-trans-2-aminocyclohexan-1-aminium di(methanesulfonyl)azanide and its 0.11-hydrate

C. Wölper, N. Anwar, N. Gulzar, P. G. Jones and A. Blaschette

The title compound, C6H15N2+·C2H6NO4S2-, crystallizes as a 0.11-hydrate, (I), in the space group C2; the asymmetric unit consists of two cations (one of each enantiomer), one anion on a general position, two half anions, each with the N atom on a twofold axis, and approximately one fifth of a water molecule. The general anion departs significantly from the usual conformation: it lacks one of the typical `W'-shaped sequence of O-S-N-S-O atoms. The compound also crystallizes in the solvent-free form, (II), in the space group P21/c, with one formula unit in the asymmetric unit. Both compounds form ribbons of hydrogen-bonded cation dimers parallel to the b axis. In (I), there are two independent ribbons of opposite chirality, each involving one anion on a special position, and these ribbons are connected by hydrogen bonds to the anion on a general position, resulting in a layer structure parallel to (100). In (II), the chains are connected by hydrogen bonds, and again a layer structure parallel to (100) results.

thumbnail of article figure
Acta Cryst. (2011). C67, o283-o287    [doi:10.1107/S0108270111024322]

N-(tert-Butoxycarbonyl)-[alpha]-aminoisobutyryl-[alpha]-aminoisobutyric acid methyl ester: two polymorphic forms in the space group P21/n

H. G. Gebreslasie, Ø. Jacobsen and C. H. Görbitz

The title compound (systematic name: methyl 2-{2-[(tert-butoxycarbonyl)amino]-2-methylpropanamido}-2-methylpropanoate), C14H26N2O5, (I), crystallizes in the monoclinic space group P21/n in two polymorphic forms, each with one molecule in the asymmetric unit. The molecular conformation is essentially the same in both polymorphs, with the [alpha]-aminoisobutyric acid (Aib) residues adopting [varphi] and [psi] values characteristic of [alpha]-helical and mixed 310- and [alpha]-helical conformations. The helical handedness of the C-terminal residue (Aib2) is opposite to that of the N-terminal residue (Aib1). In contrast to (I), the closely related peptide Boc-Aib-Aib-OBn (Boc is tert-butoxycarbonyl and Bn is benzyl) adopts an [alpha]L-PII backbone conformation (or the mirror image conformation). Compound (I) forms hydrogen-bonded parallel [beta]-sheet-like tapes, with the carbonyl groups of Aib1 and Aib2 acting as hydrogen-bond acceptors. This seems to represent an unusual packing for a protected dipeptide containing at least one [alpha],[alpha]-disubstituted residue.

thumbnail of article figure
Acta Cryst. (2011). C67, o301-o305    [doi:10.1107/S0108270111024632]

Concomitant polymorphism in the stereoselective synthesis of a [beta]-benzyl-[beta]-hydroxyaspartate analogue

S. Mekki, V. Rolland, S. Bellahouel, A. van der Lee and M. Rolland

Two concomitant polymorphs, (I) and (II), of a [beta]-benzyl-[beta]-hydroxyaspartate analogue [systematic name: dibenzyl 2-benzyl-2-hydroxy-3-(4-methylphenylsulfonamido)succinate], C32H31NO7S, crystallize from a mixture of ethyl acetate and cyclohexane at ambient temperature. The structure of (I) has triclinic (P\overline{1}) symmetry and that of (II) monoclinic (P21/c) symmetry. Both crystal structures are made up of a stacking of homochiral racemic dimers (2S,3S and 2R,3R) which are internally connected by a similar R22(9) hydrogen-bonding pattern consisting of intermolecular N-H...O and O-H...O hydrogen bonds. The centroid of the racemic dimer lies on an inversion centre. The main structural difference between the two polymorphs is the conformational orientation of two of the four aromatic rings present in the molecule. Polymorph (II) is found to be twinned by reticular merohedry with twin index 3 and twin fractions 0.854 (1) and 0.146 (1).

thumbnail of article figure
Acta Cryst. (2011). C67, o310-o314    [doi:10.1107/S0108270111023845]

Solvatomorphism in (E)-2-(2,6-dichloro-4-hydroxybenzylidene)hydrazinecarboximidamide

J. Gutierrez, R. Eisenberg, G. Herrensmith, T. Tobin, T. Li and S. Long

The structures of orthorhombic (E)-4-(2-{[amino(iminio)methyl]amino}vinyl)-3,5-dichlorophenolate dihydrate, C8H8Cl2N4O·2H2O, (I), triclinic (E)-4-(2-{[amino(iminio)methyl]amino}vinyl)-3,5-dichlorophenolate methanol disolvate, C8H8Cl2N4O·2CH4O, (II), and orthorhombic (E)-amino[(2,6-dichloro-4-hydroxystyryl)amino]methaniminium acetate, C8H9Cl2N4O+·C2H3O2-, (III), all crystallize with one formula unit in the asymmetric unit, with the molecule in an E configuration and the phenol H atom transferred to the guanidine N atom. Although the molecules of the title compounds form extended chains via hydrogen bonding in all three forms, owing to the presence of different solvent molecules, those chains are connected differently in the individual forms. In (II), the molecules are all coplanar, while in (I) and (III), adjacent molecules are tilted relative to one another to varying degrees. Also, because of the variation in hydrogen-bond-formation ability of the solvents, the hydrogen-bonding arrangements vary in the three forms.

thumbnail of article figure
Acta Cryst. (2011). C67, m304-m306    [doi:10.1107/S0108270111033051]

Weak C-H...Cl-Pd interactions toward conformational polymorphism in trans-dichloridobis(triphenylphosphane)palladium(II)

R. S. Corrêa, A. E. Graminha, J. Ellena and A. A. Batista

A new triclinic polymorph of the title compound, [PdCl2(C18H15P)2], has two independent molecules in the unit cell, with the Pd atoms located on inversion centres. One molecule has an eclipsed conformation, whereas the second molecule adopts a gauche conformation. The molecules with a gauche conformation are involved in weak intermolecular C-H...Cl-Pd interactions with symmetry-related molecules. It is suggested that C-H...Cl-Pd interactions are mainly responsible for the existence of conformational differences, which contribute to the polymorph formation. In the crystal, there are layers of eclipsed and gauche molecules separated by normal van der Waals interactions.

thumbnail of article figure
Acta Cryst. (2011). C67, o354-o358    [doi:10.1107/S0108270111027867]

1,2-Bis[(pyridin-2-ylmethyl)sulfanyl]ethane and its dimorphic hydrochloride salt

A. Lennartson and C. J. McKenzie

Although having been described as a liquid in the literature for 41 years, 1,2-bis[(pyridin-2-ylmethyl)sulfanyl]ethane, C14H16N2S2, (I), has now been obtained as monoclinic crystals via a new and convenient method of purification. Molecules of (I) are located on crystallographic inversion centres and are held together by C-H...N and C-H...S interactions, resulting in the formation of a three-dimensional network structure. In addition, two polymorphs of the corresponding hydrochloride salt, 2-[({2-[(pyridin-1-ium-2-ylmethyl)sulfanyl]ethyl}sulfanyl)methyl]pyridin-1-ium dichloride, C14H18N2S22+·2Cl-, (II) and (III), have been isolated. Molecules of (II) and (III) have similar conformations and are located on inversion centres. Both polymorphs form three-dimensional networks through N-H...Cl, C-H...Cl and C-H...S interactions. The structure of (III) displays voids of 35 Å3.

thumbnail of article figure
Acta Cryst. (2011). C67, i50-i52    [doi:10.1107/S0108270111033713]

A tetragonal form of dysprosium orthomolybdate at room temperature

S. Dorzhieva, I. Chumak, A. Sarapulova, D. Mikhailova, J. Bazarova and H. Ehrenberg

In the present tetragonal modification of dysprosium orthomolybdate, Dy2(MoO4)3, the Dy, one Mo and one O atom are located on a mirror plane with Wyckoff symbol 4e, while another Mo atom is located on a fourfold inverse axis, Wyckoff symbol 2a. A single crystal was selected from a polycrystalline mixture of the Dy2O3-ZrO2-MoO3 system and was stable at room temperature for at least three months. The structure refinement does not indicate the presence of Zr on the Dy sites (to within 1% accuracy). Thus, the stabilization of the tetragonal form is due to disordered positions for a second O atom and split positions for a third O atom that also maintain the DyO7 coordination, which is not expected for short Dy-O distances [2.243 (6)-2.393 (5) Å].

thumbnail of article figure
Acta Cryst. (2011). C67, o391-o393    [doi:10.1107/S0108270111033245]

A new polymorph of succinylcholinium diiodide: comparison of succinylcholinium structures

R. Pazout, J. Maixner, M. Dusek and B. Kratochvíl

The title compound {systematic name: trimethyl[2-({4-oxo-4-[2-(trimethylazaniumyl)ethoxy]butanoyl}oxy)ethyl]azanium diiodide}, C14H30N2O42+·2I-, is a salt of the succinylcholinium cation. There is one formula unit in the asymmetric unit, represented by two anions and two halves of two cations which lie on centres of inversion. The component species are stabilized by electrostatic interactions, and C-H...I and C-H...O hydrogen bonds are also present.

thumbnail of article figure
Acta Cryst. (2011). C67, o394-o396    [doi:10.1107/S0108270111039230]

A variable-temperature study of 1,2-bis(dimethylamino)-1,2-bis(2,6-dimethylanilino)diborane

A. S. Batsanov, G. Bramham, N. C. Norman and C. A. Russell

The title compound, C20H32B2N4, is monoclinic at ambient temperature but triclinic (pseudo-monoclinic) below 150 K. The structures of the two phases, determined at 200 and 120 K, respectively, are very similar, the molecular symmetry being crystallographic C2 and approximate (local) C2, respectively. There is significant [pi] conjugation within each N-B-N moiety, but none between them or between the N-B-N and arene moieties.

thumbnail of article figure
Acta Cryst. (2011). C67, o405-o408    [doi:10.1107/S0108270111037930]

Concomitant but disappearing: two polymorphs of 1,4-bis(tribromomethyl)benzene

P. G. Jones, H. Hopf, A. Silaghi and C. Näther

The title compound, C8H4Br6, (I), initially crystallized from deuterochloroform as the comcomitant polymorphs (Ia) (prisms, space group P21/n, Z = 2) and (Ib) (hexagonal plates, space group C2/c, Z = 4). The molecules in both forms display crystallographic inversion symmetry. All further attempts to crystallize the compound led exclusively to (Ib), so that (Ia) may be regarded as a `disappearing polymorph'. Surprisingly, however, the density of (Ia) is greater than that of (Ib). The only significant difference between the molecular structures is the orientation of the CBr3 groups. The molecular packing of both structures is largely determined by Br...Br interactions, although (Ia) also displays a C-H...Br hydrogen bond and both polymorphs display one Br...[pi] contact. For (Ia), six of the eight contacts combine to form a tube-like substructure parallel to the a axis. For (Ib), the two shortest Br...Br contacts link `half' molecules consisting of C-CBr3 groups to form double layers parallel to (001) in the regions z [asymptotically equal to] {1 \over 4}, {3 \over 4}.

thumbnail of article figure
Acta Cryst. (2011). C67, o428-o434    [doi:10.1107/S0108270111038868]

A new polymorph and two pseudopolymorphs of pyrimethamine

M. Tutughamiarso and M. Bolte

Due to its donor-acceptor-donor site, the antimalarial drug pyrimethamine [systematic name: 5-(4-chlorophenyl)-6-ethylpyrimidine-2,4-diamine] is a potential component of a supramolecular synthon. During a cocrystallization screen, one new polymorph of solvent-free pyrimethamine, C12H13ClN4, (I), and two pseudopolymorphs, pyrimethamine dimethyl sulfoxide monosolvate, C12H13ClN4·C2H6OS, (Ia), and pyrimethamine N-methylpyrrolidin-2-one monosolvate, C12H13ClN4·C5H9NO, (Ib), were obtained. In (I), (Ia), (Ib) and the previously reported polymorph, the pyrimethamine molecules exhibit similar conformations and form R22(8) dimers stabilized by a pair of N-H...N hydrogen bonds. However, the packing arrangements are completely different. In (I), the dimers are connected by two additional N-H...N hydrogen bonds to form ribbons and further connected into a two-dimensional network parallel to (100), while layers containing N-H...Cl hydrogen-bonded pyrimethamine ribbons are observed in the packing of the known polymorph. In the two pseudopolymorphs, two pyrimethamine molecules are linked to form R22(8) dimers and the solvent molecules are connected to the dimers by R23(8) interactions involving two N-H...O hydrogen bonds. These arrangements are connected to form zigzag chains by N-H...Cl interactions in (Ia) and to form ribbons by N-H...N interactions in (Ib). Unexpectedly, a reaction between pyrimethamine and N-methylpyrrolidin-2-one occurred during another cocrystallization experiment from a solvent mixture of N-methylpyrrolidin-2-one and dimethyl sulfoxide, yielding solvent-free 5,5'-{[5-(4-chlorophenyl)-6-ethylpyrimidine-2,4-diyl]bis(azanediyl)}bis(1-methylpyrrolidin-2-one), C22H27ClN6O2, (II). In the packing of (II), the pyrimethamine derivatives are N-H...O hydrogen bonded to form ribbons. A database study was carried out to compare the molecular conformations and hydrogen-bonding interactions of pyrimethamine.

thumbnail of article figure
Acta Cryst. (2011). C67, o461-o463    [doi:10.1107/S0108270111043952]

Polymorphic form IV of olanzapine

R. Thakuria and A. Nangia

2-Methyl-4-(4-methylpiperazin-1-yl)-10H-thieno[2,3-b][1,5]benzodiazepine, C17H20N4S, commonly known as olanzapine, is a psychotropic agent that belongs to the thienobenzodiazepine class of drugs. A new polymorph form IV was obtained upon attempted cocrystallization with nicotinamide in a 1:1 ratio from an ethyl acetate solution. Two butterfly-like molecules form centrosymmetric dimers stabilized by weak C-H...[pi] interactions between the 4-methylpiperazin-1-yl fragment and the benzene/thiophene aromatic system. Form IV consists of a herringbone arrangement of dimers, whereas the previously reported form II has parallel dimers. Both crystal structures are sustained by an N-H...N hydrogen bond.

thumbnail of article figure
Acta Cryst. (2011). C67, o484-o486    [doi:10.1107/S0108270111043575]

Two tautomeric polymorphs of 2,6-dichloropurine

M. E. García-Rubiño, D. Choquesillo-Lazarte, M. C. Núñez and J. M. Campos

Two polymorphs of 2,6-dichloropurine, C5H2Cl2N4, have been crystallized and identified as the 9H- and 7H-tautomers. Despite differences in the space group and number of symmetry-independent molecules, they exhibit similar hydrogen-bonding motifs. Both crystal structures are stabilized by intermolecular N-H...N interactions that link adjacent molecules into linear chains, and by some nonbonding contacts of the C-Cl...[pi] type and by [pi]-[pi] stacking interactions, giving rise to a crossed two-dimensional herringbone packing motif. The main structural difference between the two polymorphs is the different role of the molecules in the [pi]-[pi] stacking interactions.

thumbnail of article figure
Acta Cryst. (2011). C67, o487-o491    [doi:10.1107/S0108270111041825]

Sulfapyridine (polymorph III), sulfapyridine dioxane solvate, sulfapyridine tetrahydrofuran solvate and sulfapyridine piperidine solvate, all at 173 K

J. Pratt, J. Hutchinson and C. L. Klein Stevens

The X-ray crystal structures of solvates of sulfapyridine have been determined to be conformational polymorphs. 4-Amino-N-(1,2-dihydropyridin-2-ylidene)benzenesulfonamide (polymorph III), C11H11N3O2S, (1), 4-amino-N-(1,2-dihydropyridin-2-ylidene)benzenesulfonamide 1,3-dioxane monosolvate, C11H11N3O2S·C4H8O2, (2), and 4-amino-N-(1,2-dihydropyridin-2-ylidene)benzenesulfonamide tetrahydrofuran monosolvate, C11H11N3O2S·C4H8O, (3), crystallized as the imide form, while piperidin-1-ium 4-amino-N-(pyridin-2-yl)benzenesulfonamidate, C5H12N+·C11H10N3O2S-, (4), crystallized as the piperidinium salt. The tetrahydrofuran and dioxane solvent molecules in their respective structures were disordered and were refined using a disorder model. Three-dimensional hydrogen-bonding networks exist in all structures between at least one sulfone O atom and the aniline N atom.

thumbnail of article figure
Acta Cryst. (2011). C67, o492-o495    [doi:10.1107/S0108270111045951]

Two polymorphs of N1,N4-bis(5-hydroxypenta-1,3-diynyl)-N1,N4-diphenylbenzene-1,4-diamine

H. Tabata, N. Kubo and T. Okuno

The title compound, C28H20N2O2, forms two conformational polymorphs, (I) and (II), where the molecular structures are similar except for the orientation of the two hydroxy groups. In (I), which was obtained by slow evaporation from chloroform, the two hydroxy groups have an anti conformation. The molecules form a sheet structure within the ac plane, where the hydroxy groups form zigzag hydrogen bonds. In (II), which was obtained by slow evaporation from acetonitrile, the two hydroxy groups have a syn conformation. The molecules form a double-sheet structure within the ab plane, where the hydroxy groups form 4-helix hydrogen bonds.

thumbnail of article figure
Acta Cryst. (2011). C67, o496-o499    [doi:10.1107/S010827011104786X]

Polymorphs of anhydrous theophylline: stable form IV consists of dimer pairs and metastable form I consists of hydrogen-bonded chains

D. Khamar, R. G. Pritchard, I. J. Bradshaw, G. A. Hutcheon and L. Seton

The structure of a previously unreported polymorph of anhydrous theophylline (1,3-dimethyl-3,7-dihydro-1H-purine-2,6-dione), C7H8N4O2, has been determined at 100 K and shown to have monoclinic symmetry with Z' = 2. The structure is named form IV and experimental observation indicates that this is the stable form of the material. The molecular packing consists of discrete hydrogen-bonded dimers similar to that observed in the monohydrate structure. The structure of form I has also been determined and consists of hydrogen-bonded chains.