Novel Cu(II) complexes of bithiazole: structure and biological study

Abstract

The reaction of copper(II) bromide with 2,2′-dimethyl-4,4′-bithiazole (dm4bt) affords a dimer complex, [{CuBr(dm4bt)}2(µ-Br)2] (1), in CH3OH/CH3CN; and a monomer complex, [Cu(dm4bt)Br2(DMSO)] (2), in DMSO. Monomer copper(II) complex [Cu(4bt)Br2(DMSO)] (3) also resulted from the treatment of the copper salt with 4,4′-bithiazole (4bt) in DMSO. The complexes were characterized by elemental analysis, IR, UV and X-ray crystallography. The interaction of monomeric complexes 2 and 3 with calf thymus DNA (CT DNA) has been explored by using absorption, emission and thermal denaturation, where they exhibit high interaction ability with CT DNA, with intrinsic binding constants K b of 1.58 × 105 and 1.24 × 105 M−1 at 298 K, for complexes 2 and 3, respectively. Furthermore, the intermolecular interaction between the mentioned copper complexes and bovine serum albumin (BSA) under imitated physiological conditions was investigated using UV–Vis and fluorescence. Tryptophan-quenching experiment illustrated that both complexes strongly bind BSA, with dynamic quenching constants of about 1 × 105 M−1 s−1 at 298 K, and a single class of binding site for the complexes on BSA.