Mn(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and Co(II) complexes of 1-phenyl-1H-tetrazole-5-thiol: Synthesis, spectral, structural characterization and thermal studies

Abstract

The new complexes [Mn(ptt)2(en)2] (1), [Ni(ptt)2(en)2] (2), [Cu(ptt)2(en)2] (3), [Zn(ptt)2(en)] (4), [Hg(ptt)2(en)] (5), [Cd(ptt)2(en)2] (6), [Cd2(μ-ptt)2(ptt)2(bpy)2] (7) and [Co(phen)3](ptt)2 (8) have been synthesized from 1-phenyl-1H-tetrazole-5-thiol (Hptt), containing en/bpy/phen as a co-ligand. The complexes have been characterized by elemental analyses, IR, UV–Vis and single crystal X-ray data. The ligand is covalently bonded through a deprotonated tetrazole ring nitrogen atom in complexes 1–4 and via a thiolato sulfur atom in complexes 5 and 6, in which the ligand acts as uninegative monodentate. Complex 7 is dimeric via thiolato bridging, in which two terminal ligands act as uninegative monodentate while the other two ligands act as uninegative bridging bidentate. Complex 8 is ionic, in which the cationic part, [Co(phen)3]2+, is held by two tetrazole anions through hydrogen bonding. The structures of the complexes are stabilized through weak intermolecular C–H⋯S, N–H⋯S and N–H⋯N interactions. Complexes 5 and 7 are also stabilized by π⋯π interactions. Thermogravimetric analyses of the complexes have been investigated by TG-DTA, which indicate the metal sulfide/oxide as the final residue. All the complexes contain extended hydrogen bonding, providing supramolecular frameworks. The bioefficacy of complexes 1–4 and 8 has been examined against the growth of bacteria in vitro to evaluate their anti-microbial potential.