Bio-affinity of copper(II) complexes with nitrogen and oxygen donor ligands: Synthesis, structural studies and in vitro DNA and HSA interaction of copper(II) complexes

•Synthesis and characterization of copper(II) complexes with N,O-donor ligands•Binding affinity of copper(II) complexes with Human Serum Albumin•DNA binding and cleavage activities of copper (II) complexes•Biophysical method for quantitative evaluation of the thermodynamics of interaction

Reported herein the binding affinity between Human Serum Albumin and the DNA binding and cleavage activity of three copper(II) complexes, [Cu(phen)(o-van)ClO4] (1), [Cu(phen)(gly)]ClO4 (2) and [Cu(L1)2(H2O)2] (3) wherein 1 and 2 are synthesized with 1,10-phenanthroline (phen) and co-ligands (o-van: o-vanillin; gly: glycine) and 3 with a ligand 2-hydroxy-3-methoxybenzylidene-4H-1,2,4-triazol-4-amine (H1L1). Complex 2 crystallizes in monoclinic (P21/n) space group shows square pyramidal geometry. The complex 3 crystallizes in monoclinic (P21/a) space group. All the three complexes exhibit binding affinity towards the transport protein Human Serum albumin (HSA). Quantitative evaluation of the thermodynamics of interaction and the results obtained from fluorescence spectroscopy suggest that metal coordinated glycynate, o-vanillin and perchlorate groups have a major role to play in the binding process, the latter two being stronger in the binding of complex 1. The coordinated water in complex 3 also plays an important role in the binding, which makes binding of complex 3 with HSA stronger than that of complex 2. Experimental results indicate that the binding affinity of the complexes towards CT-DNA is in the order 1 > 3 > 2 implying that complex 1 binds stronger than complex 3 and 2.The DNA cleaving activity of all the three complexes was explored in the presence of reactive oxygen compound, H2O2. All the three complexes have primarily shown the DNA cleaving activity.

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