Coordination studies of copper(II), nickel(II), cobalt(II) and zinc(II) salts with pyridyl-tetrazole ligands containing alkyl or alkyl halide pendant arms

The reaction of 2-(2H-tetrazol-5-yl)pyridine (L1) with 1,n-dibromoalkane (n = 3, 4, 6 or 8) results in the formation of the isomers 2-(n ''-bromoalkyl-(1-tetrazol-5-yl)pyridine (L2A-D) and 2-(n ''-bromoalkyl-(2-tetrazol-5-yl)pyridine (L3A-D). The reaction of L1 with 1-bromoalkanes also resulted in the formation of isomeric materials, namely 2-(n ''-alkyl-(1-tetrazol-5-yl)pyridine (L4A-C) and 2-(n ''-alkyl-(2-tetrazol-5-yl)pyridine (L5A-C). Complexation reactions of these ligands with the transition metal salts CuCl2 center dot 2H(2)O, Co(NCS)(2), NiCl2 center dot 2H(2)O and ZnCl2 were carried out in methanol and resulted in complexes containing a 1:1 metal:ligand stoichiometry except in the cases of the cobalt complexes where a 1:2 metal:ligand stoichiometry was obtained. The H-1 NMR spectra of the zinc complexes showed that the ligands containing the pendant arm in the 2-N position of the tetrazole ring bind the zinc ion more strongly than those containing the pendant arm in the 1-N position. The X-ray structures of two cobalt salts, Co(L5A)(2)(NCS)(2) and Co(L5C)(2)(NCS)(2), are also discussed. (C) 2013 Elsevier Ltd. All rights reserved.