Synthesis, structural elucidation, DNA-binding and anti-oxidant activities of centrosymmetric paddlewheel copper carboxylate complexes

Abstract Synthesis, structural characterization and preliminary biological relevance of four new copper carboxylate complexes (1-4) has been presented here. The complexes have been synthesized by direct treatment of the substituted phenyl acetate and pyridine ligands in aqueous medium. The complexes were stable indefinitely with excellent yield and were characterized using spectroscopic and single crystal XRD techniques. FTIR spectroscopy revealed the bridging bidentate coordination mode for the carboxylate moiety in accordance to the actual structure revealed by XRD. Moreover, UV-Visible spectroscopic and cyclic voltammetric studies helped in their characterization and yielded signals which were typical of the copper(II) complexes. Successfully solved single crystal XRD data showed binuclear paddlewheel structures for all the complexes with both copper ions linked through four OCO bridges of ortho-methoxy phenyl acetate (1-3) and ortho-methyl-meta-nitrophenyl acetate (4). The geometry around each copper was distorted square pyramidal where the apical positions are occupied by meta-bromopyridine (1), meta-methylpyridine (2) and DMSO (3 and 4) molecules. The complexes exhibited excellent DNA-binding activity majorly via intercalation as revealed by four experimental techniques in line with the in silico studies. Their anti-oxidant activity was also comparable to that of the ascorbic acid. Complexes 1 and 4 exhibited significant anti-bacterial activity against Micrococcus luteus and Staphylococcus aureus. These preliminary findings indicated the biological potential of the synthesized complexes.