Comparative Study of three Mononuclear Vanadium‐Aromatic 1, 2‐Diol Complexes: Structure, Characterization and Anti‐Proliferating Effects Against Cancer Cells

Three mononuclear vanadium complexes containing aromatic 1, 2‐diols (catechol and naphthalene‐2, 3‐diol) ligands,[V IV O(cat) 2 ][1, 3‐HPDA] 2 · CH 3 OH ( 1 ), [V IV O(N‐2, 3‐D) 2 ][1, 3‐H 2 PDA] ( 2 ), and [V V O 2 (N‐2, 3‐D)(1, 3‐HPDA)] · 1, 3‐PDA ( 3 ) (cat = catechol, N‐2, 3‐D = naphthalene‐2, 3‐diol, 1, 3‐PDA = 1, 3‐propanediamine) were synthesized and characterized by X‐ray diffraction, IR and UV/Vis spectroscopy, and cyclovoltammetry. X‐ray analysis reveals that the spatial frameworks of complexes 1 – 3 are all constructed by hydrogen bonds donated by [1, 3‐H n PDA] n + ( n = 1, 2) cation, forming distinct chain structures. Complexes 1 and 2 are both in the non‐chiral form of VO(L) 2 , but 2 crystallizes in the chiral space group ( P 6 5 22), due to the symmetry element of spiral axis, whereas complex 3 contains both enantiomers of chiral VO 2 (L 1 )(L 2 ) units, but crystallizes in the non‐chiral space group ( P $\bar{1}$ ). The electrochemical behavior of the three complexes is studied in comparison with that of the free ligands. Complex 1 shows a pair of potentials assigned to the redox behavior of vanadium, while complexes 2 and 3 exhibit no such redox potentials. Pharmaceutical screening of complexes 1 – 3 were carried out against three representative cancer cell lines: A‐549 (lung cancer), Bel‐7402 (liver cancer) and HCT (colonic cancer) by MTT [3‐(4, 5‐dimethylthiazoyl‐2‐yl)‐2, 5‐diphenyltetrazolium bromide] assay. The results show that the vanadium‐catechol complex 1 exhibits more obvious anti‐proliferating effects against the three cell‐lines, whereas the two vanadium‐N‐2, 3‐D complexes 2 and 3 basically display no such effects.