Bifendate, a synthetic anti-hepatitis drug, exhibits polycrystalline mode phenomena with 2 polymorphs reported (forms A and B). Single crystals of the known crystalline form B and 3 new crystallosolvates involving bifendate solvated with tetrahydrofuran (C), dioxane (D), and pyridine (E) in a stoichiometric ratio of 1:1 were obtained and characterized by X-ray crystallography, thermal analysis, and Fourier transform infrared (FT-IR) spectroscopy. The differences in molecular conformation, intermolecular interaction and crystal packing arrangement for the four polymorphs were determined and the basis for the polymorphisms was investigated. The rotation of single bonds resulted in different orientations for the biphenyl, methyl ester and methoxyl groups. All guest solvent molecules interacted with the host molecule via an interesting intercalative mode along the [1 0 0] direction in the channel formed by the host molecules through weak aromatic stacking interactions or non-classical hydrogen bonds, of which the volume and planarity played an important role in the intercalation of the host with the guest. The incorporation of solvent-augmented rotation of the C–C bond of the biphenyl group had a striking effect on the host molecular conformation and contributed to the formation of bifendate polymorphs. Moreover, the simulated powder X-ray diffraction (PXRD) patterns for each form were calculated on the basis of the single-crystal data and proved to be unique. The single-crystal structures of the four crystalline forms are reported in this paper.

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Two tetranuclear copper(II) complexes bridged by asymmetrical N,N 0 -bis(substituted)oxamides have been synthesized and characterized as [Cu 4 (dmapob) 2 (Me 2 bpy) 2 ]-(pic) 2 Á6H 2 O (1) and [Cu 4 (oxbe) 2 (dabt) 2 ](pic) 2 (2), where H 3 dmapob and H 3 oxbe denote N-benzoato-N 0 -[3-(dimethylamino)propyl]oxamido and N-benzoato-N 0 -(2-aminoethyl)oxamide, respectively; and Me 2 bpy, dabt, and pic represent 4,4 0 -dimethyl-2,2 0 -bipyridine 2,2 0 -diamino-4,4 0 -bithiazole, and 2,4,6-trinitrophenol, respectively. Complex 1 was characterized by elemental analyses, IR and electronic spectra, and single-crystal X-ray diffraction. Its structure consists of two asymmetrical binuclear copper(II) units linked by carboxyl bridges into a circular tetranuclear copper(II) complex with an embedded center of inversion. The copper(II) centers are in square-planar and distorted squarepyramidal environments. Hydrogen bonds and aromatic stacking interactions link the tetranuclear copper(II) fragments into a 3D supramolecular structure. The interactions of complexes 1 and 2 with herring sperm DNA (HS-DNA) were investigated by electronic and fluorescence spectra and viscosity measurements. Both complexes bind to HS-DNA via the intercalative mode, and complex 2 displays a significant binding propensity to HS-DNA.

The title complex, {[Cu(2)(C(14)H(16)N(3)O(4))(C(6)H(6)N(4)S(2))]NO(3)·0.6H(2)O}(n), is a one-dimensional copper(II) coordination polymer bridged by cis-oxamide and carboxylate groups. The asymmetric unit is composed of a dinuclear copper(II) cation, [Cu(2)(dmapob)(dabt)](+) {dmapob is N-(2-carboxylatophenyl)-N'-[3-(dimethylamino)propyl]oxamidate and dabt is 2,2'-diamino-4,4'-bithiazole}, one nitrate anion and one partially occupied site for a solvent water molecule. The two Cu(II) ions are located in square-planar and square-pyramidal coordination environments, respectively. The separations of the Cu atoms bridged by oxamide and carboxylate groups are 5.2053 (3) and 5.0971 (4) Å, respectively. The complex chains are linked by classical hydrogen bonds to form a layer and then assembled by π-π stacking interactions into a three-dimensional network. The influence of the terminal ligand on the structure of the complex is discussed.

The title complex, [CuNi(C(13)H(16)N(3)O(3))(C(10)H(8)N(2))(2)(H(2)O)]ClO(4), has a cis-oxamide-bridged heterobinuclear cation, with a Cu···Ni separation of 5.3297 (6) Å, counterbalanced by a disordered perchlorate anion. The Cu(II) and Ni(II) cations are located in square-pyramidal and octahedral coordination environments, respectively. The complex molecules are assembled into a three-dimensional supramolecular structure through hydrogen bonds and π-π stacking interactions. The influence of the two types of metal cation on the supramolecular structure is discussed.