New copper(II) complexes with (Z)-N′-{(2-hydroxynaphthalen-1-yl}methylene)acetohydrazide]: X-ray structure, Hirshfeld analysis, X-band electron paramagnetic resonance spectra, TD-DFT calculations and superoxide dismutase mimetic activity

Abstract

In this paper, two ternary copper(II) complexes having the general formula [Cu(HL)(X)] have been synthesized by reacting equimolar solutions of Cu(ClO4)2·6H2O, HL and X (HL = (Z)-N′-{(2-hydroxynaphthalen-1-yl}methylene)acetohydrazide], X = 2,9-dimethyl-1,10-phenanthroline (DMPHEN) and BZI = benzimidazole) in methanol. The complexes have been characterized by microanalysis (C, H and N), magnetic susceptibility and spectral (IR, UV–Vis and X-band epr) measurements. The molecular structures of both complexes have been determined by single-crystal X-ray diffraction analysis. Most interestingly, complex 1, which contains of both hydrogen bonding and π∙∙∙π (chelate-chelate) interactions, forms a supramolecular architecture. Hirshfeld analysis and fingerprint plots verified weak CH∙∙∙π and π∙∙∙π non-covalent interactions that lead both complexes to build supramolecular architectures. To relate to the experimental environment, TD-DFT calculations have been carried out. The TD-DFT findings suggest that transitions in the lowest-energy region are mixed absorption bands with d-d and ligand to metal transitions (LMCT). Room temperature magnetic measurements have been performed to disclose the paramagnetic nature of the complexes. An X-band epr spectral study has been carried out to verify the paramagnetic and bonding behavior of both complexes. The stability of the metal center was explored using electrochemical (cyclic voltammetry and differential pulse voltammetry) techniques. In addition, the superoxide dismutase activities of both complexes have been evaluated using nitro blue tetrazolium assays at pH 7.4. The SOD activity data rank among the best values reported for low molecular weight mononuclear copper(II) complexes reported in the literature.