Spectral, in vitro antiradical and antimicrobial assessment of copper complexes containing tridentate Schiff base derived from dihydroxybenzene functionality with diaminoethylene bridge

Abstract

The reaction of copper salts with Schiff base ligand: [4-[(1E)-N-{2-[(Z)-(4-methoxybenzylidene)amino]ethyl}ethanimidoyl]benzene-1,3-diol] derived from the condensation of ethylenediamine, 2-hydroxy-1-(4-hydroxyphenyl)ethenone and 4-methoxybenzaldehyde afforded copper complexes bearing chloride, bromide, thiocyanate, nitrate, and acetate. The complexes exhibited crystalline features and excellent thermal stability up to 450 °C. The powder X-ray diffraction pattern suggests a well-defined crystalline structure with average crystallite sizes of < 52 nm. The scavenging ability of 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid radicals by the synthesized compounds was studied for their antioxidant potential and screening for antimicrobial activity by p-iodonitrotetrazolium chloride colorimetric assay. The investigated assays suggest that the synthesized compounds are potent antiradical and antimicrobial agents. Research highlights An eco-friendly method was followed for the synthesis of functionalized tridentate ONN Schiff base ligand. Five Schiff base copper(II) complexes were synthesized bearing chloride, bromide, thiocyanate, nitrate, and acetate. Structural features were characterized by CHN, PXRD, TG-DTG, NMR, UV–Vis, and FT-IR spectro-analytical techniques. Schiff base ligand and its copper complexes showed good to excellent DPPH and ABTS radicals scavenging capability. Cu(II) complexes of Schiff base ligand (MEB) showed good antimicrobial properties via the p-iodonitrotetrazolium chloride (INT) colorimetric assay.