Synthesis, crystal structure, and antimicrobial activity of a series of cobalt(III) Schiff base complexes

A series of six new mononuclear Schiff base complexes, 1–6 of cobalt(III) of the general formula, [CoLX] or its adduct with methanol, is reported. The pentadentate Schiff base ligand (H2L) was obtained by the condensation of N-(3-aminopropyl)-N-methylpropane-1,3-diamine with 1-(2-hydroxyphenyl)ethanone (H2L1) or 1-(2-hydroxyphenyl)propan-1-one (H2L2). X stands for the pseudohalides, N3–, N(CN)2−, and NCS–. The complexes have been synthesized by the reaction of equimolar amounts of cobalt(II) nitrate with H2L1 or H2L2 in the presence of the respective pseudohalide in methanol medium. All the complexes have been characterized by microanalytical, spectroscopic, single crystal XRD (except 3), and other physicochemical studies. Structural studies reveal that the central Co(III) ion in 1, 2, 4, 5, and 6 adopts a distorted octahedral geometry with a CoN4O2 chromophore. Weak intermolecular H-bonding and/or π-interactions are operative in these complexes to bind the molecular units. The antimicrobial activity of all the complexes and their constituent Schiff bases has been tested against some common bacteria and fungi.