Madhukar Hemamalini

1-[3,5-Bis(4-fluoro­phen­yl)-4,5-dihydro-1H-pyrazol-1-yl]ethanone

In the asymmetric unit of the title compound, C17H14F2N2O, there are three independent molecules (A, B and C) which differ slightly in the relative orientations of the two fluorophenyl rings. In molecules A and C one of the fluorophenyl rings is disordered over two positions, with occupancy ratios of 0.72 (2):0.28 (2) for molecule A and 0.67 (2):0.33 (2) for molecule C. The dihedral angle between the two fluorophenyl rings in the independent molecules lie in the range 70.3 (3)–84.0 (3)°. In the crystal structure, the molecules are linked via intermolecular C—H⋯O and C—H⋯F hydrogen bonds and π⋯π stacking interactions [centroid–centroid distance = 3.7508 (13) Å], forming a three-dimensional network.

Methyl 4,6-bis­(4-fluoro­phen­yl)-2-oxo­cyclo­hex-3-ene-1-carboxyl­ate

The 3-cyclohexene units adopt envelope conformations in each of the two independent molecules that comprise the asymmetric unit of the title compound, C20H16F2O3. The dihedral angles between the two fluorophenyl rings are 79.7 (2) and 73.7 (2)° in the two molecules. In one of the molecules, two C—H groups of the cyclohexene ring are disordered over two sets of sites in a 0.818 (13):0.182 (13) ratio, the major and minor components corresponding to the two enantiomeric forms of the molecule. Weak intermolecular C—H⋯O interactions help to stabilize the crystal structure.

3,3′-[1,2-Phenyl­enebis(methyl­ene)]bis­(1-ethyl­benzimidazolium) dibromide

In the title molecular salt, C26H28N4 2+·2Br−, the central benzene ring makes dihedral angles of 76.75 (11) and 82.40 (10)° with the pendant benzimidazole rings. The corresponding angle between the benzimidazole rings is 57.03 (9)°. In the crystal, the cations and anions are linked via C—H⋯Br hydrogen bonds, forming sheets lying parallel to the bc plane. The crystal structure also features weak C—H⋯π interactions.

1-(4,4′′-Difluoro-5′-meth­oxy-1,1′:3′,1′′-terphenyl-4′-yl)ethanone

In the title compound, C21H16F2O2, the central benzene ring is inclined at dihedral angles of 30.91 (8) and 46.88 (7)° to the two terminal fluoro-substituted rings. The dihedral angle between the two terminal fluoro-subsituted rings is 68.34 (8)°. An intramolecular C—H⋯O hydrogen bond generates an S(6) ring motif. The crystal structure is stabilized by weak C—H⋯π interactions.

Investigation of supramolecular synthons and structural characterisation of aminopyridine-carboxylic acid derivatives

BackgroundCo-crystal is a structurally homogeneous crystalline material that contains two or more neutral building blocks that are present in definite stoichiometric amounts. The main advantage of co-crystals is their ability to generate a variety of solid forms of a drug that have distinct physicochemical properties from the solid co-crystal components. In the present investigation, five co-crystals containing 2-amino-6-chloropyridine (AMPY) moiety were synthesized and characterized.ResultsThe crystal structure of 2-amino-6-chloropyridine (AMPY) (I), and the robustness of pyridine-acid supramolecular synthon were discussed in four stoichiometry co-crystals of AMPY…BA (II), AMPY…2ABA (III), AMPY…3CLBA (IV) and AMPY…4NBA (V). The abbreviated designations used are benzoic acid (BA), 2-aminobenzoic acid (2ABA), 3-chlorobenzoic acid (3CLBA) and 4-nitrobenzoic acid (4NBA). All the crystalline materials have been characterized by 1HNMR, 13CNMR, IR, photoluminescence, TEM analysis and X-ray diffraction. The supramolecular assembly of each co-crystal is analyzed and discussed.ConclusionsExtensive N---H · · · N/N---H · · · O/O---H · · · N hydrogen bonds are found in (I-V), featuring different supramolecular synthons. In the crystal structure, for compound (I), the 2-amino-6-chloropyridine molecules are linked together into centrosymmetric dimers by hydrogen bonds to form homosynthon, whereas for compounds (II-V), the carboxylic group of the respective acids (benzoic acid, 2-aminobenzoic acid, 3-chlorobenzoic acid and 4-nitrobenzoic acid) interacts with pyridine molecule in a linear fashion through a pair of N---H · · · O and O---H · · · N hydrogen bonds, generating cyclic hydrogen-bonded motifs with the graph-set notationR228, to form heterosynthon. In compound (II), another intermolecular N---H · · · O hydrogen bonds further link these heterosynthons into zig-zag chains. Whereas in compounds (IV) and (V), these heterosynthons are centrosymmetrically paired via N---H · · · O hydrogen bonds and each forms a complementary DADA [D = donor and A = acceptor] array of quadruple hydrogen bonds, with graph-set notationR238, R228 and R238.

Synthesis and characterization of lead(II) complexes with substituted 2,2′-bipyridines, trifluoroacetate, and furoyltrifluoroacetonate

Two substituted 2,2′-bipyridine lead(II) complexes, [Pb(5,5′-dm-2,2′-bpy)(tfac)2] n (1) (5,5′-dm-2,2′-bpy = 5,5′-dimethyl-2,2′-bipyridine and tfac = trifluoroacetate) and [Pb2(4,4′-dmo-2,2′-bpy)2(ftfa)4] (2) (4,4′-dmo-2,2′-bpy = 4,4′-dimethoxy-2,2′-bipyridine and ftfa = furoyltrifluoroacetonate), have been synthesized and characterized by elemental analysis, IR, 1H NMR, and 13C NMR spectroscopies, thermal behavior, and X-ray crystallography. Complexes 1 and 2 are 1D coordination polymer and dinuclear complex, respectively. The supramolecular features in these complexes are guided by weak directional intermolecular interactions.

3,3′-[1,2-Phenylenebis(methylene)]bis(1-heptylbenzimidazolium) dibromide monohydrate

In the title salt, C36H48N4 2+·2Br−·H2O, the central benzene ring makes dihedral angles of 84.77 (9) and 69.92 (7)° with the adjacent imidazole rings. In the crystal, one of the heptyl groups is disordered over two sets of sites with an occupancy ratio of 0.474 (5):0.526 (5). In the crystal, the cations, anions and water molecules are connected via intermolecular O—H⋯Br, C—H⋯Br and C—H⋯O hydrogen bonds, forming a three-dimensional network.

3-Benzyl-2-phenyl-1,3-thia-zolidin-4-one.

In the title compound, C16H15NOS, the thiazolidine ring, which is essentially planar [maximum deviation = 0.071 (2) Å], makes dihedral angles of 88.01 (8) and 87.21 (8)° with the terminal phenyl rings. The dihedral angle between the phenyl rings is 49.45 (5)°. In the crystal, molecules are linked by a weak intermolecular C—H⋯O hydrogen bond, forming a supramolecular chain along the b axis. Furthermore, the crystal packing is stabilized by a weak C—H⋯π interaction.

2-Amino-4-methyl-pyridinium 4-nitro-benzoate.

In the title salt, C6H9N2 +·C7H4NO4 −, the nitro group of the 4-nitrobenzoate anion is twisted by 7.66 (10)° from the attached ring. In the crystal structure, the 2-amino-4-methylpyridinium cations and 4-nitrobenzoate anions are linked via a pair of N—H⋯O hydrogen bonds to form a ribbon-like structure along the c axis. The ribbons are crosslinked into a three-dimensional framework by C—H⋯O hydrogen bonds.

2,3-Diaminopyridinium 2-hydroxybenzoate

In the title compound, C5H8N3 +·C7H5O3 −, the pyridine N atom is protonated. In the 4-hydroxybenzoate anion, the carboxylate group is twisted slightly out of the benzene ring plane by an angle of 3.77 (5)°. The protonated N atom and one of the two amino groups are hydrogen-bonded to the 4-hydroxybenzoate anion through a pair of N—H⋯O hydrogen bonds, forming an R 2 2(8) ring motif. The crystal structure is further stabilized by O—H⋯O and C—H⋯O hydrogen bonds and π–π interactions involving the pyridinium rings [centroid–centroid distance of 3.6277 (5) Å], leading to the formation of a three-dimensional network.