Spectroscopic studies and biological evaluation of some transition metal complexes of Schiff-base ligands derived from 5-arylazo-salicylaldehyde and thiosemicarbazide

Abstract

Synthesis and spectroscopic characterization of Schiff-base complexes of Cu(II), Ni(II), and Mn(II) resulting from condensation of salicylaldehyde derivatives with thiosemicarbazide [PHBT = 1-(5-(2-phenyldiazenyl)-2-hydroxybenzylidene)thiosemicarbazide, CHBT = 1-(5-(2-(2-chlorophenyl)diazenyl)-2-hydroxybenzylidene)thiosemicarbazide, and MHBT = 1-(5-(2-p-tolyldiazenyl)-2-hydroxybenzylidene)thiosemicarbazide] are discussed. The solid complexes were confirmed by elemental analysis (CHN), molar conductance, and mass spectra. Important infrared (IR) spectral bands corresponding to the active groups in the three ligands, 1H-NMR and UV-Vis spectra and thermogravimetric analysis were performed. The dehydration and decomposition of [Cu(PHBT)(H2O)], [Ni(PHBT)(H2O)] · 2H2O, [Mn(PHBT)(H2O)] · H2O, [Cu(CHBT)(H2O)], [Ni(CHBT)(H2O)] · H2O, [Mn(CHBT)(H2O)] · H2O, [Cu(MHBT)(H2O)], [Ni(MHBT)(H2O)] · 2H2O, and [Mn(MHBT)(H2O)] · 2H2O complexes were studied. The ligands are tridentate forming chelates with 1 : 1 (metal : ligand) stoichiometry. The molar conductance measurements of the complexes in DMSO indicate non-electrolytes. The biological activities of the metal complexes have been studied against different gram positive and gram negative bacteria.