Syntheses, characterization and crystal structures of eight Cd(II) carboxylates containing 3,5-dimethylpyrazole

Abstract

Eight new complexes, namely [Cd(Hdmpz)2(L1)20.5H2O]2 (1) (Hdmpz=3,5-dimethylpyrazole, L1=trichloroacetate), [Cd(Hdmpz)2(L2)2]·H2O (2) (L2=indole-3-acetate), Cd(Hdmpz)2(L3)2 (3) (L3=4-methylbenzoate), Cd(Hdmpz)4(L4)2 (4) (L4=3-methylbenzoate), Cd(Hdmpz)4(L5)2 (5) (L5=4-methoxybenzoate), Cd(Hdmpz)2(L6)2 (6) (L6=2-chloronicotinate), Cd(Hdmpz)(HL7)2 (7) (HL7=2-hydroxy-5-(phenyldiazenyl)benzoate) and [Cd2(Hdmpz)6(L8)2]·(Hdmpz)2 (8) (L8=o-phthalate) have been prepared by the self-assembly of Cd ions, 3,5-dimethylpyrazole and carboxylic acids at room temperature. All the complexes were characterized by elemental analysis, IR spectra, TG and single crystal X-ray diffraction analysis. The X-ray studies revealed that these complexes display mononuclear to dinuclear structures, with an octahedral geometry around each cadmium ion. The 3,5-dimethylpyrazole ligand in all the compounds is coordinated only in a monodentate fashion by its neutral N group. In 2, 3 and 6, the carboxylate groups behave as chelating bidentate ligands. In 4 and 5, the carboxylate groups act as monodentate ligands. The COO− group in 1 is coordinated to the Cd centre in both monodentate and bridging bidentate modes. The carboxylates in 7 coordinate to the Cd centre in tridentate chelating bridging and bidentate bridging fashions, simultaneously, while in 8 there exists a tridentate bridging carboxylate ligand. Based on the X-ray crystallographic study, extensive intra- and intermolecular non-covalent interactions, such as classical hydrogen bonds, CH–Cl, CH3–Cl, Cl⋯Cl, Cl⋯O, CH–N, CH3–N, C–H⋯O, CH3⋯O, C–H⋯π, CH2⋯π, CH3–π and π–π interactions, are analyzed. These compounds display different structures, such as a 0D discrete mononuclear arrangement, sheet, 3D network, and 3D layer network. The thermal stabilities for 1–8 were examined and the results show that the complexes display good thermal stability.