New VIV, VIVO, VVO, and VVO2 Systems: Exploring their Interconversion in Solution, Protein Interactions, and Cytotoxicity

The synthesis and characterization of one oxidoethoxidovanadium(V) [(VO)-O-V(L-1)(OEt)] (1) and two nonoxidovanadium(IV) complexes, [V-IV(L2-3)(2)] (2 and 3), with aroylhydrazone ligands incorporating naphthalene moieties, are reported. The synthesized oxido and nonoxido vanadium complexes are characterized by various physicochemical techniques, and their molecular structures are solved by single crystal X-ray diffraction (SC-XRD). This revealed that in 1 the geometry around the vanadium atom corresponds to a distorted square pyramid, with a O4N coordination sphere, whereas that of the two nonoxido V-IV complexes 2 and 3 corresponds to a distorted trigonal prismatic arrangement with a O4N2 coordination sphere around each "bare" vanadium center. In aqueous solution, the (VO)-O-V moiety of 1 undergoes a change to (VO2)-O-V species, yielding [(VO2)-O-V(L-1)](-) (1'), while the nonoxido V-IV-compounds 2 and 3 are partly converted into their corresponding (VO)-O-IV complexes, [(VO)-O-IV(L2-3)(H2O)] (2' and 3'). Interaction of these (VO2)-O-V, (VO)-O-IV, and V-IV systems with two model proteins, ubiquitin (Ub) and lysozyme (Lyz), is investigated through docking approaches, which suggest the potential binding sites: the interaction is covalent for species 2' and 3', with the binding to Glu16, Glu18, and Asp21 for Ub, and His15 for Lyz, and it is noncovalent for species 1', 2, and 3, with the surface residues of the proteins. The ligand precursors and complexes are also evaluated for their in vitro antiproliferative activity against ovarian (A2780) and prostate (PC3) human cancer cells and in normal fibroblasts (V79) to check the selectivity of the compounds for cancer cells.