3 years ago

Construction of nine non-covalently-bonded zinc(II) and cadmium(II) supramolecules containing the mixed-ligands of 3,5-dimethylpyrazole and carboxylates: Their synthesis and characterization

Construction of nine non-covalently-bonded zinc(II) and cadmium(II) supramolecules containing the mixed-ligands of 3,5-dimethylpyrazole and carboxylates: Their synthesis and characterization
The present report pertains to the synthesis and characterization of nine novel mixed-ligand complexes, Zn(Hdmpz)2(L1)2 (1) (Hdmpz = 3,5-dimethylpyrazole, L1 = 2-furoate), Cd(Hdmpz)4(L2)2 (2) (L2 = 1-hydroxy-2-naphthoate), Zn(Hdmpz)2(L3)2 (3) (L3 = 5-bromosalicylate), Cd(Hdmpz)2(L4) (4) (L4 = 4-nitro-phthalate), Zn(Hdmpz)2(L5)2 (5) (L5 = 3-(2-chloro-phenylcarbamoyl)-acrylate), Zn(Hdmpz)2(L6)2 (6) (L6 = 3-m-tolylcarbamoyl-acrylate), Cd(Hdmpz)2(L6)2 (7), Zn(Hdmpz)2(L7)2 (8) (L7 = 3-p-tolylcarbamoyl-acrylate) and [Cd(Hdmpz)2(L7)2]2·2H2O (9). The resulting complexes were formulated from elemental analysis, IR spectra and single crystal X-ray diffraction analysis. The TGA of all the complexes was also evaluated. The X-ray studies revealed that these complexes display mononuclear to binuclear structures with a tetrahedral geometry around each Zn atom and an octahedral geometry around each Cd atom. The Hdmpz ligands in all the compounds are coordinated only in a monodentate fashion through its neutral N atom. The carboxylate ligands in 1, 2, 3, 5, 6 and 8 act only as unidentate coordination ligands, while the carboxylate ligands in 4 and 7 have a chelating bidentate coordination mode. Compound 9 contains both unidentate bridging and chelating bidentate coordinated carboxylate groups. The uncoordinated O atom of the COO group in 1, 2 and 3 forms an intramolecular hydrogen bond with the N–H group of the Hdmpz, compound, 4 bears an intramolecular N–H⋯O hydrogen bond between the pyrazole ligand and the coordinated O atom. In 5, 6, 7 and 8, there are intramolecular N–H⋯O hydrogen bonds from the N–H unit of the Hdmpz ligand and the O atom of the CONH group. In 9, the N–H⋯O hydrogen bonds from the –H unit of the Hdmpz ligand, the O atom of the CONH group and the coordinated O atom of the COO group were found. In addition, in the compound 9 there exists an intra-anion N–H⋯O hydrogen bond between the coordinated O atom and the CONH unit, displaying a S1 1(7) ring. The intricate intra- and intermolecular classical hydrogen bonds, Br–Br, CH3–Br, CH–N, C–H⋯O, CH3⋯O, O⋯π(C), Cl–π, C–H⋯Cπ, C–H⋯π, CH3–π and π–π associations are elucidated from the X-ray crystallographic studies, which turn the discrete complexes into high-dimensional ordered supramolecular structures.

Publisher URL: www.sciencedirect.com/science

DOI: S0277538717306381

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