Spectroscopic, quantum chemical calculations, antioxidant, anticancer, antimicrobial, DNA binding and photo physical properties of bioactive Cu(II) complexes obtained from trifluoromethoxy aniline Schiff bases

Abstract In this study, new three Schiff base ligands and their Cu(II) complexes: 1 [Cu(L1)2], 2 [Cu(L2)2] and 3 [Cu(L3)2], where HL1-HL3 represent Schiff base ligands (HL1 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-6‑chloro-4-fluorophenol, HL2 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-3,5-dimethoxy-phenol and HL3 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-5-(diethylamino)phenol) were synthesized. The structural features were confirmed from their micro analytical, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), UV–visible, mass, magnetic susceptibility measurements, ESR and thermal analysis. The spectroscopic approaches proposed a square planar geometry for all Cu(II) complexes. The stability of the binary metal(II) complexes has been calculated from quantum chemical parameters using highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energies. All the tested complexes preferably bind to CT-DNA via intercalation mode as resulted from UV spectroscopy and EB competition assay studies. In addition, the metal complexes exhibited good cleavage ability against the pBR322 DNA in the presence and absence of H2O2 as well as UV light. The antioxidant activity of 1–3 was evaluated by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical with reference of ascorbic acid. Of these, complex 1 show good antioxidant activity. The in vitro cytotoxicity studies of the ligands and their complexes against human lung (A549) and breast (MCF7) cancer cell lines showed significant activity. The Schiff base ligands and their metal complexes were screened for their biological activities and are found to be the complexes have higher activities than the free Schiff bases.