Comparison of two binuclear vanadium–catecholate complexes: Synthesis, X-ray structure and effects in cancer cells

Two binuclear vanadium–catecholate complexes [Et3NH]2[VVO2(μ-cat)]2(1) and [Et3NH]2[VVO2(μ-N-2,3-D)]2(2) (cat = catechol, N-2,3-D = naphthalene-2,3-diol) have been synthesized and characterized by X-ray diffraction, IR, UV–vis spectroscopy and cyclic voltammetry (CV). X-ray analysis reveals that the structures of complexes 1 and 2 are both in the anion form of V 2 V O 4 ( L ) 2 2 - . Et3N works as counter-ions and connects the main frame by hydrogen bonding. The electrochemical behavior of the two complexes is studied in comparison to that of the free ligands and the two complexes display different redox potentials. Pharmaceutical screenings of complexes 1 and 2 have been made against two representative cancer cell-lines A-549 (lung cancer) and Bel-7402 (liver cancer) by MTT assay. The inhibition of cell proliferation was determined 72 h after cells were exposed to the tested compounds at a concentration of 5 μg/mL. Complex 1 exhibits well inhibition ratio against both two cell-lines (76.28% and 75.94%), while 2 displays positive and negative effect (65.36% and −68.82%) respectively. In association with X-ray and electrochemistry, a preliminary analysis about the possible inhibitory mechanism is provided.