Structure elucidation {spectroscopic, single crystal X-ray diffraction and computational DFT studies} of new tailored benzenesulfonamide derived Schiff base copper(II) intercalating complexes Comprehensive biological profile {DNA binding, pBR322 DNA cleavage, Topo I inhibition and cytotoxic activity}
Abstract
New tailored copper(II)-based intercalating complexes [Cu(L)] (1) and [Cu(L)] (2) were synthesized from Schiff base scaffold HL and HL(E)-4-(2-((2-hydroxy-3-methoxybenzylidene)amino)ethyl)benzenesulfonamide and (E)-4-(2-((2-hydroxybenzylidene)amino)ethyl)benzenesulfonamide, respectively. The structure elucidation of complexes 1 and 2 was carried out by employing various spectroscopic techniques viz., FT-IR, UV-vis, ESI-MS, EPR and single X-ray crystal diffraction studies. The complexes 1 and 2 were crystallized in monoclinic P2/n and triclinic P-1 space group, respectively possessing square planar geometry around Cu(II) coordinated with N,O-donor Schiff base ligands. An analysis of Hirshfeld surfaces of complexes 1 and 2 were performed to ascertain different intra and intermolecular non-covalent interactions (H-bonding, CH⋯ πetc.) responsible for the stabilization of crystal lattices. Calculations based on Density functional theory (B3LYP/DFT), have been carried out to obtain energies of Frontier molecular orbitals. Comparative in vitro binding profile of complexes 1 and 2 with ct-DNA was evaluated employing various biophysical techniques viz., UV-vis, fluorescence, circular dichroism and cyclic voltammetry which suggested non-covalent intercalative binding mode with more avid binding propensity of complex 1 compared to complex 2. The cleavage experiments of complex 1 was performed by gel electrophoretic assay which revealed efficient cleavage mediated via oxidative pathway. Furthermore, topoisomerase I enzymatic activity of complex 1 was carried out employing gel electrophoretic assay which demonstrated significant inhibitory effects at a low concentration of 25 µM. The cytotoxic potential of complex 1 was analyzed by SRB assay on a panel of selected human cancer cell lines which revealed selective activity for MCF-7 (breast cancer) cell line with GI = 16.21 µg/ml.