Synthesis, structure and electrochemistry of Co(III) complexes with an unsymmetrical Schiff base ligand derived from 2-aminobenzylamine and pyrrole-2-carboxaldehyde

Abstract

A series of cobalt(III) complexes with a new unsymmetrical tetradentate Schiff base ligand N,N’-bis(pyrrol-2-ylmethylene)-2-aminobenzylamine, H 2pyrabza, formed by the condensation of 2-pyrrole carboxaldehyde and 2-aminobenzylamine, has been synthesized and characterized by elemental analyses, IR, UV–Vis and 1H NMR spectroscopy. These complexes have the general formula trans-[Co III(L)(amine) 2]X {L 2− = pyrabza, and amine = N-methylimidazole (N-MeIm) ( 1), 3-methylpyridine (3-Mepy) ( 2), 4-methylpyridine (4-Mepy) ( 3), pyridine (py) ( 4), X = BPh 4 - }. The structure of compound 1 has been determined by X-ray crystallography. The geometry around the central cobalt ion is distorted octahedral. The electrochemical behavior of these complexes was also investigated. The reduction potential of Co(III), ranging from −0.79 V for 1 to −0.44 V for 4, shows a relatively good correlation with the σ-donor ability of the axial ligands.