Synthesis, single crystal structures, DFT and in vitro anti oxidant superoxide dismutase studies of copper(II) complexes derived from the di-(2-picolyl)amine and co-ligands: Promising antioxidants

Abstract

Three new copper(II) complexes, [Cu(DPA)(ClO4)2(H2O)]MAP 1, [Cu(DPA)(ImH)(ClO4)2] 2 and [Cu2(DPA)2(2COO−)(ClO4)2]H2O 3 (where, DPA = di-(2-picolyl)amine, MPA = 2-methoxyacetophenone, ImH = Imidazole and 2COO− = oxalate anion), have been synthesized and characterized using various physico-chemical techniques. DPA is a tridentate ligand with NNN donors atoms and imidazole is a monodentate ligand whereas, oxalate anion is a bridging ligand. Single crystal X-ray analysis reveals that 1–3 are neutral complexes. The X-band Epr spectral study in polycrystalline at RT and in DMSO solution at LNT have been analyzed. To examine the stability of complexes, density functional theory (DFT) calculations were performed. The obtained quantum chemical parameters like electron affinity, ionization potential, electronegativity, electrophilicity and global hardness and softness were discussed within the frame work of electronic structures and principles known as maximum hardness, minimum polarizability and minimum electrophilicity principles. Hirshfeld surface analysis showed that the supramolecular structures of the complexes 1–3 is stabilized mainly by CH⋯π, lp⋯π and various hydrogen bonding intermolecular interactions. Complex 3 shows ferromagnetic interaction, with J = +1.5 cm−1, due to perchlorate bridging anion complex. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) support the electrochemical features of these complexes. The Hirshfeld surface analysis exhibited short-range forces of the hydrogen bonds in all studied complexes. In addition, antioxidant superoxide dismutase activity measurements of these complexes were also performed and discussed. The increased SOD activity of 1 can be assigned due to presence of labile coordinated water molecule. The results of SOD activity reveal that the coordination geometries have significant effect on the SOD catalytic activity.