Synthesis, structure, spectroscopic, and DNA binding properties of Co(III) and Ni(II) complexes with ((E)-2-(amino((pyridin-2-ylmethylene)amino)methylene)maleonitrile)

Two new complexes, [Co(L)(2)]Cl(MeOH)(2) (1) and [Ni(L)(2)](4)EtOH (2) (L=(E)-2-(amino((pyridin-2-ylmethylene)amino)methylene)maleonitrile), were synthesized and characterized by X-ray crystallography, IR, UV, and fluorescence spectroscopy. According to X-ray crystallographic studies, each metal was six-coordinate with six nitrogens from two ligands. Both complexes form two-dimensional supramolecular networks via hydrogen bonding and - interactions. Ultraviolet and visible spectra showed that absorptions arise from -, MLCT, and d-d electron transitions. Fluorescence spectroscopy revealed moderate intercalative binding of these two complexes with EB-DNA, with apparent binding constant (K-app) values of 9.14x10(5) and 3.20x10(5)M(-1) for Co(III) and Ni(II) complexes, respectively. UV-visible absorption spectra showed that the absorption of DNA at 260nm was quenched for 2 but quenched then improved for 1 with addition of complexes, tentatively attributed to the effect of the combined intercalative binding and electrostatic interaction for 1.