Structure, DNA-binding interaction and antitumour activity of two novel complexes coordinated by tridentate 1,3-bis(benzimidazol-2-yl)-2-oxapropane ligand

Two novel DNA-intercalating complexes, [Cd(hipa)(bbiop)](n) (1) and [Ni(ada)(bbiop)](n)2H(2)O (2) with hipa, ada and potentially tridentate ligand bbiop (bbiop, 1,3-bis(benzimidazol-2-yl)-2-oxa-propane; hipa, 5-hydroxyisophthalate; ada, aniline-N,N-diacetate), have been synthesised under hydrothermal methods and structurally characterised by single crystal X-ray diffraction analysis, elemental analysis, UV-vis spectrum and fluorescent spectrum. The bbiop ligand exists as chelating-tridentate (1)-((3)-N-1, N-2, O-6) coordination fashion. In addition, their in vitro cytotoxicities towards four selected tumour cell lines have been evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. Complex 1 exhibits the most dramatic inhibitory effect on MG-63, and its inhibition rate is higher than that of its free ligands, H(2)bbiop and hipa, indicating significantly enhanced effect after forming complex. On the basis of the combination of UV-vis absorption and fluorescence titrations, complex 1 can interact with the base pairs of double-helical DNA via an intercalative mode with intrinsic binding constant, K-b, of 4.62x10(7), presenting the high DNA-binding affinity.