Ternary Copper (II) complex based chemical probes for DNA targeting: Cytotoxic activity under visible light

Among the bio-metals, copper derivatives of O, N, S donor salicylaldehyde thiosemicarbazones have been obtained large interest due to their potential biological applications. Multisubstituted thiosemicarbazone ligand HL derived, new ternary Cu (II) complexes of [Cu(L)(bpy)] (1) and [Cu(L)(phen)] (2) (where, bpy is 2,2 '-bipyridine and phen is 1,10-phenanthroline) have been synthesized and characterized using different physico-chemical techniques. Complexes 1 and 2 are structurally characterized by single crystal X-ray diffraction analysis, which reveals the trigonal bipyramidal distorted square based pyramid geometry of both the complexes 1 and 2 with ONS-donor thiosemicarbazone bonded at the upper plane. The ground state electronic structures of complexes 1 and 2 have been investigated by using DFT/B3LYP theoretical evaluation with 6-31G (d,p) and LANL2DZ basis set. The affinity towards DNA and human serum albumin has been evaluated using computational docking analysis and complex 2 exposes significant binding ability towards DNA and human serum albumin, because of its immense hydrophobicity. Consequently, complex 2 have higher antimicrobial in addition to the cytotoxic activity than complex 1 and free ligand HL under visible light. Along with, their apoptosis pathway of cytotoxicity has been evaluated by fluorescent microscopic analysis using acridine orange/ethidium bromide (AO/EB) stains. From these preliminary investigations, we believe that complex 2 can play a role as a more robust pharmacological agent.