Molecular hybridization approach of bio-potent CuII/ZnIl complexes derived from N, O donor bidentate imine scaffolds: Synthesis, spectral, human serum albumin binding, antioxidant and antibacterial studies

Novel bio-relevant monometallic Schiff base complexes of the type, [Cu(L-1)(2)] (1), [Zn(L-1)(2)]center dot 2H(2)O (2), [Cu(L-2)(2)]center dot 2H(2)O (3) and [Zn(L-2)(2)]H2O (4) [L-1 =(E)-3-( ( (3-chloro-4-hydroxyPhenyl)imino)methyl)naphthalen-2-ol and L-2 =(E)-2-chloro-4((1-(5-chloro-2-hydroxyphenyeethylidene)amino)phenol] were synthesized and characterized. A comparative account of analytical, spectroscopic (FT-IR, H-1 and C-13 NMR, Mass, UV-vis and EPR), thermal (TGA/DTA), XRD and SEM studies revealed a correlation between the structure and function of these biologically active molecular entities. HSA (Human serum albumin) binding profiles of the metal complexes (1-4) were monitored using biophysical techniques viz., absorbance, fluorescence, circular dichromism (CD) and foster resonance energy transfer (FRET). The intrinsic binding constant (Kb) demonstrated substantial binding propensity of L-1 linked complexes (1 and 2) in comparison to L-2 complexes (3 and 4) suggesting L-1 to be more bio-active pharmacophore due to higher planarity and conjugation as compared to L-2 ligand. The outcome of fluorescence study revealed static quenching mechanism on the basis of the quenching of HSA by the complexes (1-4). However, modifications in the secondary structure of HSA by complexes (1-4) inferred via CD measurements which revealed the enhancement of alpha-helicity (67.47% to 69.20%) with the preference order of 1 > 2 > 3 > 4. Furthermore, in-vitro antibacterial study against different bacteria and antioxidant activities against DPPH center dot and superoxide radical (O-2(-center dot)) at variable concentrations outspread discernible bio-potencies of the metal complexes as compared to free ligand scaffolds due to the chelation effect. (C) 2016 Elsevier B.V. All rights reserved.