High-valent oxovanadium metallosupramolecular species as catalysts for the oxidation of benzyl alcohol derivatives.

Coordination-driven synthesis has been successfully utilized to prepare vanadium-based metallosupramolecular species. By systematically varying synthesis methods and reaction conditions, two series of isostructural oxovanadium(v) coordination polymers [VO(SIH)(OR)] n (where SIH2- represents salicylaldehyde isonicotinoylhydrazonate, and R corresponds to CH3 (1β·0.25CH3OH), C2H5 (2α and 2β·0.25C2H5OH), C3H7 (3α), C4H9 (4α and 4β), and C5H11 (5β)), were synthesized. Additionally, a phase-pure tetranuclear compound [VO(SIH)(OCH3)]4·4CH3OH (1t·4CH3OH) was also prepared. In these compounds the [VO(SIH)] units, featuring the isonicotinoylhydrazonate heterocyclic moiety, are interconnected through V-Nisonicotinoyl coordination bonds. This linkage enables formation of the one-dimensional (1D) zig-zag chain compounds and zero-dimensional (0D) metallocycle, as determined by single crystal X-ray crystallography. This study further explored the formation and transformation of the assemblies, thereby emphasizing the influence of the ancillary OR- ligand. The compounds were also characterized by powder X-ray diffraction, chemical analysis, thermogravimetric (TGA) measurements, and spectroscopic methods (IR-ATR, UV-Vis, and NMR). The catalytic activity of vanadium coordination entities 1t and 1β was tested for the oxidation of benzyl alcohol and its derivatives, including 2-nitrobenzyl, 2-chlorobenzyl, and 2-methylbenzyl alcohol. Several oxidizing agents were used, including tert-butyl hydroperoxide (TBHP) in aqueous and decane solutions, as well as hydrogen peroxide (H2O2). The study also assessed the impact of different solvents, such as toluene, acetonitrile, and methanol, thereby enhancing the understanding of these systems.