The syntheses and characterizations of molybdenum(vi) complexes with catechol and 2,3-dihydroxynaphthalene, and the structure–effect relationship in their in vitro anticancer activities

Abstract

The reactions of (NH₄)₂Mo₂O₇·2H₂O with polyhydroxy phenols (catechol or 2,3-dihydroxynaphthalene) and ethylenediamine (en), trimethylenediamine (tn), 1,2-propanediamine (pn), triethylamine (Et₃N) respectively, in the mixed-solvent of MeCN–EtOH–amine, have resulted in five molybdenum(VI) complexes, (enH₂)[Mo^VIO₃(cat)(en)] (1), (tnH₂)[Mo^VIO₃(cat)(tn)] (2), (enH)₂[Mo^VIO₂(cat)₂](en)_0.5 (3), (pnH₂)₂[Mo^VIO₂(cat)₂] (4) and (HNEt₃)₂[Mo^VIO₂(C₁₀H₈O₂)₂] (5), of which the structural features were investigated by X-ray diffraction. MTT assay tests indicated that their inhibition ratios against human cancer cells decreased in the order: (1) ≈ (2) > (3) ≈ (4) > (5), i.e. the activities decreased when the chelation number or the size of the aromatic ligand increased, which was consistent with the Gibbs free energies (ΔG) determined from theoretical computations by Gaussian 03. The mechanisms behind this trend were discussed preliminarily.