Electrochemical transformations and photophysical, anti/prooxidant properties of triphenylantimony(V) complexes with tridentate redox-active Schiff bases

Abstract

A number of novel triphenylantimony(V) complexes with O,N,O'- or O,N,S redox-active Schiff bases (Ph3Sb(Ln) were synthesized. Compounds 1–5 were characterized by 1H, 13C NMR, IR spectroscopy, and elemental analysis. The molecular structures of complexes 1 and 2 in crystal state were established by means of single-crystal X-ray analysis. Both complexes are mononuclear hexacoordinated triphenylantimony(V) compounds containing dianionic forms of O,N,O’-coordinated ligands. The electrochemical properties of complexes 1–5 were studied. In the cathode region, stable monoanionic forms were formed for all compounds, while the electrooxidation process is irreversible for most complexes. A quasi-reversible one-electron anode stage was observed only for complex 2 with donor tert‑butyl groups. Based on electrochemical data, the energy gap ΔEel between the boundary redox orbitals of complexes varies from 2.64 to 2.95 eV, while the optical ΔE has lower values (2.75 – 2.80 eV). Triphenylantimony(V) complexes possess luminescence in solutions. The maximum luminescence intensity and quantum yields change depending on the nature of the substituents in the coordinated Schiff bases. The radical scavenging activity of new complexes was estimated in the ABTS assay. It has been found that compounds 2 and 3 with tert‑butyl or chlorine substituents in ligand have IC50 values compared with Trolox. The anti/prooxidant effects of compounds 1–5 on the process of rat liver (Wistar) homogenate lipid peroxidation and the promoted oxidative damage of the DNA were determined.