New Copper(II) and Nickel(II) Complexes with Bifunctional Tetrazolate-5-carboxylate Ligands: Syntheses, Crystal Structures, and Magnetic Properties

Four new complexes with bifunctional tetrazolate-5-carboxylate ligands of 1H-tetrazole-5-formic acid (H(2)tzf) and 1H-tetrazole-5-acetic acid (H(2)tza), namely two dinuclear [M(tzf)(H2O)(3)](2)center dot 2H(2)O (M = Cu 1, Ni 2) and two mononuclear [Cu(tzf)(2,2'-bipy)(2)]center dot 5H(2)O3 and Cu(tza)(2,2'-bipy)H(2)O4, were prepared and structurally characterized by single-crystal X-ray diffraction. Two different coordination modes of tetrazolate-5-carboxylate ligands exist: a tridentate N,O-chelated-N-bridged mode in 1 and 2, and a bidentate N,O-chelated mode in 3 and 4, which was first observed for the tetrazolate-5-carboxylate complexes. Extensive hydrogen bonds play an important role in the construction of the supramolecular network. Variable-temperature magnetic susceptibility data show the presence of antiferromagnetic interactions in 1 and 2. The thermogravimetric analyses of complexes 1-4 are also discussed.