Synthesis, crystal structures, thermal properties, and DNA-binding studies of transition metal complexes with imidazole ligands

Abstract

A new series of complexes of transition metal (Cu, Zn, Ni) perchlorate with imidazole have been synthesized and characterized by elemental analysis, infrared (IR), UV-Vis spectroscopy, and single-crystal X-ray diffraction. Based on elemental and spectral data, the complexes are M(C3H4N2) x (ClO4)2 (M = Cu, Zn, x = 4; M = Ni, x = 6; C3H4N2 = imidazole). The crystal structures of Cu(C3H4N2)4(ClO4)2 (1) and Zn(C3H4N2)4(ClO4)2 (2) show metals surrounded by four nitrogens of imidazole, while the nickel complex Ni(C3H4N2)6(ClO4)2 (3) has six nitrogens of imidazole. Intra- and inter-molecular hydrogen bonds exist between hydrogen of imidazole and oxygen of perchlorate. The thermal stabilities of 1, 2, and 3 at different heating rates (β = 5°C min−1, 10°C min−1, and 15°C min−1) show that all the complexes exhibit two thermal decomposition stages; the sequence of thermal stability is 2 > 1 > 3. 1, 2, 3, and imidazole display DNA binding ability, ascertained by UV-Vis titration.