Synthesis, physical characterization, antibacterial activity and thermodynamic studies of five coodrdinate cobalt(III) Schiff base complexes

Abstract

Some five-coordinated cobalt(III) complexes were synthesized and characterized using elemental analysis, ¹H NMR and IR spectra. The formation constants and the thermodynamic parameters were measured spectrophotometrically for the 1:1 adduct formation of [Co(Chel)(PBu₃)]ClO₄.H₂O where Chel = cd3OMesalen, cd4OMesalen, cd5OMesalen: methyl-2-{[1-methyl-2-(2-hydroxy-3-, 4-, 5-methoxyphenyl)methylidynen-itrilo]ethyl}amino-1-cyclopentene-dithiocarboxylate, as acceptors, with some linear and cyclic amines as donors, in different solvents at constant ionic strength (I = 0.1 M NaClO₄), and at various temperatures (T = 283-313 K). The results revealed that the formation constants of the Co(III) Schiff base complexes toward a given amines donor are as follow: [Co(cd4OMesalMeen)(PBu₃)]⁺ > [Co(cd3OMesalMeen)(PBu₃)]⁺ > [Co(cd5OMesalMeen)(PBu₃)]⁺. The trend of the formation constants of the donors (amines) toward a given cobalt(III) complex is as follow: Im > 4-MeIm > BzIm and n-butylamine > sec-butylamine > tert-butylamine. Also the effect of the solvents on the formation constants of a given cobalt(III) Schiff base complex toward a given donor are as follow: CH₃CN > DMF > EtOH. The ligands and their cobalt complexes have been screened for their antibacterial activities. All the free Schiff base ligands exhibit higher antibacterial activity than the cobalt(III) complexes.

KEY WORDS: Cobalt (III) Schiff base complex, Thermodynamic parameters, Amines, Antibacterial activity

Bull. Chem. Soc. Ethiop. 2016, 30(2), 209-220.

DOI: http://dx.doi.org/10.4314/bcse.v30i2.5