Synthesis, Characterization, DNA Binding-Cleavage and BSA Binding Studies of Pyridine Based Macrocyclic Binuclear Ni(II) Complexes

Five new binuclear Ni (II) complexes [Ni2L ].2ClO4 with various new unsymmetrical binucleating macrocyclic ligands were synthesized by cyclocondensation between N,N’-bis(3-formyl-5-methylsalicylidene) alkane/benzene/naphthalene-diimines (PC1-3 and 2,3-diamino -pyridine in the presence of Nickel (II) acetate and Nickel (II) perchlorate (1:1:1:1 molar ratio). Characterisation of these complexes was carried out using FT-IR, electronic and mass spectral studies and also by elemental analysis. Electrochemical properties of the complexes were studied by cyclic voltammetry. The interactions of the complexes with DNA have been measured by spectroscopic and viscosity measurements. Absorption spectroscopic investigation reveals that the Ni (II) complexes bind with DNA by intercalative binding mode, with binding constants(Kb) 1.87x10 , 0.94x10 and 0.62x10 M for the complexes 1-3 respectively. Fluorescence spectroscopic measurement shows that the Ni (II) complexes can displace ethidium bromide and bind to DNA, with binding constants(Kapp) of 2.5x10, 3.2x10and 4.3x10 M for the complexes 1-3 respectively. The interaction of the complexes with BSA has been studied by UV-Vis absorption and fluorescence spectroscopic techniques. The results indicate that the complexes have a quite strong ability to quench the fluorescence of BSA and the binding reaction is mainly a static quenching process. The complexes exhibit good binding propensity to BSA showing relatively high binding constant values. Agarose gel electrophoresis studies show that the complexes display effective DNA cleavage activity by hydrolytic mechanism.