Proton electron nuclear double resonance study of oxovanadium(IV) complexes of o-diphenolic ligands

Abstract

The vanadium (IV) complexes of catechol,3,4-dihydroxybenzoic acid, and naphthalene-2,3-diol, in water or D2O solution, have been studied by 1H electron nuclear double resonance (ENDOR) spectroscopy at 110 K. The spectra show prominent peaks which are due to ring protons adjacent to metal-bound phenolate groups, together with resonances which have contributions form more distant protons. On the whole, the 1H ENDOR pattern of the studied complexes may be satisfactorily assigned using the structural data for potassium bis (catecholato)oxovanadate(IV) and thus may be considered as diagnostic of vanadium(IV)–phenolate co-ordination. The presence of outer-sphere water molecules has also been detected in aqueous solution.