Economical Oxygenation of Olefins and Sulfides Catalyzed by New Molybdenum(VI) Tridentate Schiff Base Complexes: Synthesis and Crystal Structure

Oxidovanadium(V) Schiff Base Complexes Derived from Chiral 3-amino-1,2-propanediol Enantiomers: Synthesis, Spectroscopic Studies, Catalytic and Biological Activity

Oxidovanadium(V) complexes, [(+)VOL1-5] and [(-)VOL1-5], with chiral tetradentate Schiff bases, which are products of monocondensation of S(‒)-3-amino-1,2-propanediol or R(+)-3-amino-1,2-propanediol with salicylaldehyde derivatives, have been synthesized. Different spectroscopic methods, viz. 1H and 51V NMR, IR, UV-Vis, and circular dichroism, as well as elemental analysis, have been used for their detailed characterization. Furthermore, the epoxidation of styrene, cyclohexene, and two monoterpenes, S(‒)-limonene and (‒)-α-pinene, using two oxidants, aqueous 30% H2O2 or tert-butyl hydroperoxide (TBHP) in decane, has been studied with catalytic amounts of all complexes. Finally, biological cytotoxicity studies have also been performed with these oxidovanadium(V) compounds for comparison with cis-dioxidomolybdenum(VI) Schiff base complexes with the same chiral ligands, as well as to determine the cytoprotection against the oxidative damage caused by 30% H2O2 in the HT-22 hippocampal neuronal cells in the range of their 10-100 μM concentration.

Synthesis, Spectroscopic Characterization, Catalytic and Biological Activity of Oxidovanadium(V) Complexes with Chiral Tetradentate Schiff Bases

New oxidovanadium(V) complexes, VOL1-VOL10, with chiral tetradentate Schiff bases obtained by monocondensation reaction of salicylaldehyde derivatives with 1S,2S-(+)-2-amino-1-(4-nitrophenyl)-1,3-propanediol. All complexes have been characterized using different spectroscopic methods, viz. IR, UV-Vis, circular dichroism, one- (1H, 51V) and two-dimensional (COSY, NOESY) NMR spectroscopy, and elemental analysis. Furthermore, the catalytic ability of all compounds in the epoxidation of styrene, cyclohexene, and its naturally occurring monoterpene derivatives, i.e., S(-)-limonene and (-)-α-pinene has also been studied, using two different oxidants, i.e., aqueous 30% H2O2 or tert-butyl hydroperoxide (TBHP). In addition, the biological properties of these chiral oxidovanadium(V) compounds, but also cis-dioxidomolybdenum(VI) complexes with the same chiral Schiff bases, were studied. Their cytotoxic and cytoprotective activity studies with the HT-22 hippocampal neuronal cells revealed a concentration-dependent effect in the range of 10-100 μM. Moreover, vanadium(V) complexes, in contrast to cis-dioxidomolybdenum(VI) compounds, demonstrated higher cytotoxicity and lack of cytoprotective ability against H2O2-induced cytotoxicity.

Bottom-up approach to engineer a molybdenum-doped covalent-organic framework catalyst for selective oxidation reaction

We synthesized a readily accessible molybdenum-doped covalent-organic framework catalyst (Mo-COF) linked by a hydrazine linkage via a facile two-step bottom-up approach. This Mo-COF catalyst as an open nanochannel-reactor showed promising catalytic properties for the selective oxidation reaction.

Catalytic epoxidation activity of keplerate polyoxomolybdate nanoball toward aqueous suspension of olefins under mild aerobic conditions

Catalytic efficiency of a sphere-shaped nanosized polyoxomolybdate {Mo132} in the aerobic epoxidation of olefins in water at ambient temperature and pressure in the absence of reducing agent is exploited which resulted good-to-high yields and desired selectivity.