Substituent-dependent formation of Co(II) complexes based on phenyl-tetrazole acetic acid: from bis- to tristetrazole acetic acid

Tetrazole–carboxylates with both rigid tetrazole rings and flexible carboxylate groups provide excellent building blocks for the construction of diverse coordination architectures. We have selected a bistetrazole–carboxylate, H2btzphda [H2btzphda = 1,3-bis(tetrazol-5-yl)benzene-N2,N2′-biacetic acid] and a tristetrazole–carboxylate, H3ttzphta [H3ttzphta = 1,3,5-tris(tetrazol-5-yl)benzene-N2,N2′,N2′′-trisacetic acid] to construct new coordination compounds with CoCl2·6H2O, [Co(btzphda)(CH3OH)(H2O)2]·H2O (1), [Co3(ttzphta)2(H2O)12]·H2O (2). These coordination compounds were structurally characterized by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction. Complex 1 has a two-dimensional layer structure with (4,4) grid topology, while complex 2 has a one-dimensional beaded chain structure. The luminescence spectra of complexes 1 and 2 at room temperature in the solid state show weaker emissions than those of the corresponding free ligands. The thermogravimetric properties of complexes 1 and 2 are presented and discussed.