Synthesis and crystal structures of cytotoxic mixed-ligand copper(II) complexes with alkyl tetrazole and polypyridine derivatives

Abstract

A series of mixed-ligand copper(II) complexes {[Cu(phen)(L1)2]·H2O}n (1), [Cu(dmphen)(L1)2] (2), [Cu(bipy)(L1)2] (3) and [Cu2(dmbipy)2(L1)4] (4), where HL1 – 5-methyltetrazole, bipy – 2,2′-bipyridine, dmbipy – 4,4′-dimethyl-2,2′-bipyridine, phen – 1,10-phenanthroline, dmphen – 4,7-dimethyl-1,10-phenanthroline, has been synthesized. The complexes have been characterized by elemental analysis, IR spectroscopy and powder X-ray diffraction. Crystal structures of some complexes have been determined by single‐crystal X‐ray diffraction analysis and showed distorted tetragonal–pyramidal (1) and square pyramidal ([Cu2(bipy)2(L1)4]·DMSO and 4) geometries. The crystal structure of {(H3O)0.5[Cu(phen)(μ3-H2L2)0.5(μ3-HL2)0.5]·H2O}n (5) with alkyl tetrazole H4L2 (1,3,3,5-tetra-(1H-tetrazol-5-yl)-pentane) has also been determined. The complexes 1 and 5 have a zig-zag polymeric structure in which each copper(II) ion is coordinated by five N atoms, belonging to three different tetrazolate rings and one 1,10-phenantroline ligand, while [Cu2(bipy)2(L1)4]·DMSO and 4 are binuclear complexes. The effect of the compounds on viability of MCF-7 and Hep-2 cell lines has been investigated. Complexes 1, 2, 4 possess significant dose-dependent cytotoxic effect and 1, 2 are found to be the most cytotoxic. In addition, stability of copper(II) complexes 1–4 in water-ethanol solution and phosphate buffer saline has been investigated by UV–vis spectroscopy. The interaction of complexes 1 and 3 with calf thymus DNA (CT-DNA) has also been studied by UV–vis spectroscopy.