Synthesis and characterization of novel catalase resistant monoperoxo divanadate(V) compounds

Abstract

Oxo-bridged monoperoxo-divanadium(V) compounds in mixed-ligand environment, Na₆[V₂O₃(O₂)(NTAMSO₄)(H₂O)].2H₂O (<b>1</b>) and Na₂[V₂O₃(O₂)(gly-gly)₂(SO₄)(H₂O)].2H₂O (<b>2</b>), have been synthesized by devising an unusual synthetic methodology based on the redox reaction of sodium salt of diperoxovanadate with vanadyl sulphate in presence of respective co-ligands (NTA= nitrilotriacetic acid, gly-gly= glycylglycine) at <i>p</i>H <i>ca.</i>7.0<i> </i>(compound <b>1</b>) or <i>ca. </i>9.0 (compound<b>2</b>). Magnetic susceptibility measurement, ESR and electronic spectral data reveal that V(IV) of vanadyl is completely oxidised to V(V) during the reactions. The presence of side-on bound peroxo group, terminal as well as bridging oxo groups and un identate sulphate in the compounds are exhibited by their IR spectra. The ligands NT A in compound 1 and glyl-gly in compound 2 occur in their anionic form occupying three co-ordination positions around each of the oxo-bridged V(V) centres. The distinctive features of the compounds include their high stability towards decomposition in solution and remarkable ability to resist the action of the enzyme catalase. The compounds have been found to be inactive in the oxidation of NADH (nicotinamide adenine dinucleotide) or bromide. The dinuclear complex species appear to correspond to the inhibitor complexes formed in solution responsible for ligand induced inhibition of redox activity of a mixture of diperoxovanadate and vanadyl.