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.