1,1'-Methyl-enebis(4,4'-bipyridin-1-ium) dibromide.

The asymmetric unit of the title salt, C21H18N4 2+·2Br-, comprises half of the mol-ecule and a bromide ion. The chevron-shaped cations stack as columns in the [001] direction with suitable inter-molecular distance for π-π inter-actions. These cationic columns are further stabilized by inter-columnar C-H⋯N hydrogen bonding with the bromide ions distributed between them.

1,1'-Methyl-enebis{4-[(E)-2-(pyridin-4-yl)ethen-yl]pyridinium} dibromide dihydrate.

The chevron-shaped cations of the title hydrated salt, C25H22N4 2+·2Br-·2H2O, are arranged in back-to-back alternating directions to form a zigzag ribbon propagating along the [010] direction. Inter-molecular inter-actions comprising these ribbons are π-π inter-actions between the pyridinium and adjacent pyridyl rings, as well as O-H⋯O hydrogen bonding between water molecules and two adjacent pyridyl N atoms. Half of the cation is generated by the mirror plane. The water O atoms, the central C atom and one Br atom are located on this mirror plane while the other Br atom is on a twofold screw axis.

trans-Bis(4-amino-pyridine-κN)bis-(quin-ox-aline-2,3-di-thiol-ato-κ2 S,S')platinum(IV) dimethyl sulfoxide monosolvate.

In the structure of the title solvated complex, [Pt(C8H4N2S2)2(C5H6N2)2]·C2H6OS or trans-[Pt(4-ap)2(qdt)2]·dmso (4-ap = 4-amino-pyridyl, C5H6N2; qdt = quinoxaline-2,3-di-thiol-ate, C8H4N2S2; dmso = dimethyl sulfoxide, C2H6OS) the centrosymmetric complex exhibits Pt-S distances in agreement with other PtIV-S bond lengths found in platinum(IV) di-thiol-ene complexes. The qdt ligands have inter-molecular inter-actions with an amine hydrogen atom on a 4-ap ligand (hydrogen bonding) and have sandwich π-π inter-actions with a neighboring qdt ligand.

trans-Diamminebis(1,2-di-cyano-ethene-1,2-di-thiol-ato)platinum(IV).

The title compound, [Pt(C4N2S2)2(NH3)2], represents an octa-hedral platinum(IV) complex with two trans-ammine and two mnt (mnt = 1,2-di-cyano-ethene-1,2-di-thiol-ato) ligands. The Pt-N and Pt-S distances are consistent with those in other platinum(IV) complexes. As a result of a slight canting of the coordination of the mnt ligand to the platinum(IV) atom, the nitrile nitro-gen atoms are positioned suitably to hydrogen-bond with adjacent ammines.

Crystal structure of (3E,5E)-3,5-bis-[4-(di-ethyl-aza-nium-yl)benzyl-idene]-1-methyl-4-oxopiperidin-1-ium trichloride dihydrate: a potential biophotonic material.

In the trication of the title hydrated mol-ecular salt, C28H40N3O(3+)·3Cl(-)·2H2O, the central heterocyclic ring adopts a sofa conformation, with the exocyclic N-C bond in an equatorial orientation. The dihedral angles between the planar part of this heterocyclic ring and the two almost flat side-chain fragments, which include the aromatic ring and bridging atoms, are 28.8 (1) and 41.1 (1)°. Both di-ethyl-aza-niumyl substituents have a tetra-hedral geometry, while the dihedral angles between the above-mentioned flat part of the aryl fragments and the imaginary planes drawn through atoms C-N-C of the di-ethyl-aza-niumyl substituents are 86.3 (2) and 80.4 (1)°, respectively. In the crystal, N-H⋯Cl hydrogen bonds link the cations and anions into [100] chains. The chains are cross-linked by numerous C-H⋯O and C-H⋯Cl inter-actions, generating a three-dimensional network. One of the chloride ions is disordered over two adjacent positions in a 0.895 (4):0.105 (4) ratio.

1-Benzyl-3,5-bis-(4-chloro-benzyl-idene)piperidin-4-one.

The title compound, C(26)H(21)Cl(2)NO, crystallizes with two symmetry-independent mol-ecules (A and B) in the asymmetric unit. In both mol-ecules, the central heterocyclic ring adopts a sofa conformation. The dihedral angles between the planar part of this central heterocyclic ring [maximum deviations of 0.011 (1) and 0.036 (1) Šin mol-ecules A and B, respectively] and the two almost planar [maximum deviations of 0.020 (1) and 0.008 (1) Šin A and 0.007 (1) and 0.011 (1) in B] side-chain fragments that include the aromatic ring and bridging atoms are 20.1 (1) and 31.2 (1)° in mol-ecule A, and 26.4 (1) and 19.6 (1)° in mol-ecule B. The dihedral angles between the planar part of the heterocyclic ring and the benzyl substituent are 79.7 (1) and 53.2 (1)° in mol-ecules A and B, respectively. In the crystal, weak inter-molecular C-H⋯O hydrogen bonds link the two independent mol-ecules into dimers.

3,5-Bis(4-chloro-benzyl-idene)-1-methyl-piperidin-4-one.

In the title mol-ecule, C(20)H(17)Cl(2)NO, the central heterocyclic ring adopts a flattened boat conformation. The dihedral angles between the planar part of this central heterocyclic ring [maximum deviation = 0.004 (1) Å] and the two almost planar side-chain fragments [maximum deviations = 0.015 (1) and 0.019 (1) Å], that include the aromatic ring and bridging atoms, are 18.1 (1) and 18.0 (1)°. In the crystal, pairs of weak inter-molecular C-H⋯O hydrogen bonds link mol-ecules into inversion dimers that form stacks along the a axis. The structure is further stabilized by weak inter-molecular C-H⋯π inter-actions involving the benzene rings.

2-Amino-4-(2-methoxyphenyl)-7,7-dimethyl-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile and 2-amino-4-(2-methoxyphenyl)-7,7-dimethyl-3-nitro-4,6,7,8-tetrahydro-5H-chromen-5-one hemihydrate.

Calculations of the conformational preferences of the methoxyphenyl substituent with respect to the pyran ring have been carried out for the two title compounds, C19H20N2O3, (II), and C18H20N2O5.0.5H2O, (III). In both molecules, the heterocyclic ring adopts a flattened boat conformation and the fused cyclohexenone ring adopts a 'sofa' conformation. The dihedral angles between these two flat fragments are 14.5 (1) and 9.3 (1) degrees in (II) and (III), respectively. In both molecules, the methoxy group of the pseudo-axial aryl substituent is syn with respect to the pyran ring. The dihedral angles between the 2-methoxyphenyl rings and the flat parts of the pyran rings are 86.3 (1) and 87.0 (1) degrees, respectively. In the crystal structure of (II), intermolecular N-H...N and N-H...O hydrogen bonds link molecules into a three-dimensional framework. In the crystal structure of (III), a strong intramolecular N-H...O hydrogen bond links the flat conjugated H-N-C=C-N-O fragment into a six-membered ring. In (III), the water molecule lies on a twofold axis and forms bifurcated O-H...O hydrogen bonds with the NO2 group of the molecule. Also in (III), hydrogen bonds link the organic and water molecules into infinite tapes along the c axis.

Polymorphism and solvolysis of 2-cyano-3-[4-(N,N-diethylamino)phenyl]prop-2-enethioamide.

Two new polymorph forms, (Ia) and (Ib), of the title compound, C(14)H(17)N(3)S, and its solvate with acetonitrile, C(14)H(17)N(3)S.0.25C(2)H(3)N, (Ic), have been investigated. Crystals of the two polymorphs were grown from different solvents, viz. ethanol and N,N-dimethylformamide, respectively. The polymorphs have different orientations of the thioamide group relative to the CN substituent, with s-cis and s-trans geometry of the C=C-C=S diene fragment, respectively. Compound (Ic) contains two independent molecules, A and B, with s-cis geometry, and the solvate molecule lies on a twofold axis. The core of each molecule is slightly non-planar; the dihedral angles between the conjugated C=C-CN linkage and the phenyl ring, and between this linkage and the thioamide group are 13.4 (2) and 12.0 (2) degrees in (Ia), 14.0 (2) and 18.2 (2) degrees in (Ib), 2.3 (3) and 12.7 (4) degrees in molecule A of (Ic), and 23.2 (3) and 8.1 (4) degrees in molecule B of (Ic). As a result of strong conjugation between donor and acceptor parts, the substituted phenyl rings have noticeable quinoid character. In (Ib), there exists a very strong intramolecular steric interaction (H...H = 1.95 A) between the bridging and thioamide parts of the molecule, which makes such a form less stable. In the crystal structure of (Ia), intermolecular N-H...N and N-H...S hydrogen bonds link molecules into infinite tapes along the [1-10] direction. In (Ib), such intermolecular hydrogen bonds link molecules into infinite (101) planes. In (Ic), intermolecular N-H...N hydrogen bonds link molecules A and B into dimers, which are connected via N-H...S hydrogen bonds and form infinite chains along the c direction.

N,N-dimethyl-N'-[(1E,2E)-3-(4-nitrophenyl)prop-2-enylidene]benzene-1,4-diamine and N,N-dimethyl-4-[(1E,3E)-4-(4-nitrophenyl)buta-1,3-dienyl]-1-naphthylamine.

Syntheses and X-ray structural investigations have been carried out for the two title compounds, viz. C(17)H(17)N(3)O(2), (I), and C(22)H(20)N(2)O(2), (II). The molecular skeleton of (I) is slightly non-planar; the dihedral angles between the conjugated linkage and the p-(dimethylamino)phenyl ring, and between the linkage and the p-nitrophenyl ring are 13.0 (2) and 13.8 (2) degrees, respectively. The dihedral angle between the slightly pyramidal dimethylamine substituent and the aromatic ring is 23.3 (1) degrees. The molecular skeleton of (II) is not planar; the dihedral angles between the conjugated linkage and the naphthalene ring, and between the linkage and the substituted phenyl ring are 36.1 (2) and 2.7 (3) degrees, respectively. The dimethylamine substituent in (II) has a pyramidal geometry; the dihedral angle between this substituent and the naphthalene ring is 71.7 (1) degrees. The dihedral angle between the nitro group and the plane of the substituted phenyl ring is 9.0 (3) degrees. There is a weak intermolecular C-H.O hydrogen bond in the crystal structure of (II), which links the molecules into centrosymmetric dimers. Molecular mechanics calculations of molecular conformations have shown that the crystal environment influences the conformation more in (I) than in (II).