Synthesis, Crystal Structure, Antioxidant Activity, and DNA-Binding Studies of a Novel Ni(II) [2×2] Grid Complex with a Rigid Bistridentate Schiff Base Ligand

With a bistridentate Schiff-base ligand, N′,N′3-bis[(1E)-1-(2-pyridinyl)ethylidene)] isophthalohydrazide (H2L), a [2×2]G grid complex, [Ni4(HL)4](ClO4)4·4H2O·0.5 CH3OH (1) has been synthesized and characterized spectroscopically and crystallographically. Spectrometric titrations, ethidium bromide displacement experiments, circular dichroism spectral analysis and viscosity measurements indicate that the compound 1 strongly binds with calf-thymus DNA, presumably via intercalation mechanism. Furthermore, the antioxidant activity (superoxide and hydroxyl radical) of the ligand and its nickel(II) complex is determined by using spectrophotometer methods in vitro. Complex 1 is found to possess potent antioxidant activity and be better than standard antioxidants like mannitol.