Synthesis, structural elucidation, DNA-binding and biological activity of nickel(II) mixed ligand carboxylate complexes

Four new nickel(II) mixed ligand bicarboxylate complexes of the formulae [Ni(paranitrocinnamate)(2)(Pyridine)(2)(H2O)(2)] (1), [Ni(cinnamate) 2(Pyridine)(2) (H2O)(2)] (2), [Ni(paramethylcinnamate)(2) (2,2'-bipyridine)(H2O)(2)] (3) and the co-crystal {[Ni(para-methylcinnamate)(2)(ethylenediamine)(2)]center dot[Ni(ethylenediamine) 2](para-methylcinnamate)(2)center dot H2O} (4), have been synthesized by reacting nickel acetate and sodium salt of cinnamic acid and its substituted derivatives in aqueous medium. The ligands used in this study were cinnamic acid, 4-methylcinnamic acid, 4-nitrocinnamic acid, 2, 2'-bipyridine, pyridine and ethylenediamine. The appearance of new vibrational bands for Ni-N and Ni-O (550-480 cm(-1), 430-410 cm(-1)) in the IR spectra indicated formation of nickel(II) carboxylate mixed ligands complexes. Single crystal X-ray analysis confirmed distorted octahedral geometry for all the complexes 1-4. Complex 4 is a co-crystal with unique properties. Viscometery and UV-Visible spectroscopy studies were carried out to find out the DNA-binding ability of all synthesized complexes. By using these techniques the binding constant of the order of 10(4) M-1 and negative value for Delta G were calculated showing spontaneity of complex-DNA binding. All the synthesized complexes exhibited significant antibacterial as well as antifungal inhibition activities against three bacterial and three fungal strains. These preliminary findings herald a big hope for the further exploration of these and structurally similar complexes. (C) 2021 Elsevier B.V. All rights reserved.