Microwave synthesis and spectral, thermal and antimicrobial activities of some novel transition metal complexes with tridentate Schiff base ligands

Abstract

Some novel Schiff base metal complexes of Cr(III), Co(II), Ni(II) and Cu(II) derived from 2-[(5-bromo-2-hydroxybenzylidene)amino]pyridin-3-ol (BSAP) and {5-chloro-2-[(2-hydroxynaphthylidene)amino]phenyl}-phenylmethanone (HNAC) were synthesized by conventional as well as microwave methods. These compounds were characterized by elemental analysis, FT-IR, FAB-mass, molar conductance, electronic spectra, ESR, magnetic susceptibility, thermal, cyclic voltammetry, electrical conductivity and XRD analyses. Analytical data revealed that all the complexes exhibited 1:1 (metal:ligand) ratio with coordination number 4 or 6. IR data showed that the ligand coordinates with the metal ions in a tridentate manner. FAB-mass and thermal data showed degradation pattern of the complexes. The thermal behaviour of metal complexes showed that the hydrated complexes lose water molecules of hydration in the first step; followed by decomposition of ligand molecules in the subsequent steps. The crystal system, lattice parameter, unit cell volume and number of molecules in unit cell in the lattice of complexes were determined by XRD analysis. XRD patterns indicate crystalline nature for the complexes. The solid state electrical conductivity of the metal complexes was also measured. Solid state electrical conductivity studies reflect semiconducting nature of the complexes. The Schiff base and metal complexes displayed a good activity against the Gram-positive bacteria; Staphylococcus aureus and Gram-negative bacteria; Escherichia coli and fungi Aspergillus niger and Candida albicans. The antimicrobial results also indicate that the metal complexes displayed better antimicrobial activity as compared to the Schiff bases.