Oxidovanadium(V) complexes with chiral tetradentate Schiff bases: Synthesis, spectroscopic characterization, catalytic and biological activity

Abstract

New mononuclear oxidovanadium(V) complexes, [(−)VOL1–10] and [(+)VOL1–4], with chiral tetradentate Schiff bases have been obtained by monocondensation of salicylaldehyde derivatives and optically active amino alcohols, i.e. 1R,2R-(−)-2-amino-1-phenyl-1,3-propanediol or 1S,2S-(+)-2-amino-1-phenyl-1,3-propanediol. All complexes have been characterized by elemental analysis, circular dichroism, UV–vis, IR, 1D (1H, 51V) and 2D (COSY, NOESY) NMR spectroscopy. The catalytic activity studies have also been performed for all complexes in the epoxidation of styrene, cyclohexene and two monoterpenes, i.e. S(−)-limonene and (−)-α-pinene, using aqueous 30 % H2O2 or tert-butyl hydroperoxide (TBHP) as the terminal oxidant. In addition, biological properties of these chiral oxidovanadium(V) compounds, as well as cis-dioxidomolybdenum(VI) complexes with the same chiral Schiff bases, were studied in relation to their cytoprotective activity against the oxidative damage generated exogenously by 30 % hydrogen peroxide in the HT-22 hippocampal neuronal cells. The latter compounds have revealed distinct cytoprotective properties causing the highest increase in the viability of HT-22 cells. Concentration dependent effect in the range of 10-100 μM concentration of the investigated compounds has also been observed.