Histidine-containing bisperoxovanadium(V) compounds: Insight into the solution structure by an ESI-MS and V-51-NMR comparative study

ESI mass spectrometry and V-51-NMR spectroscopy have been used to study the reactions occurring between bisperoxo vanadates and a number of histidine and histidine-like ligands, in aqueous alcoholic solutions. Coordination of one and two molecules of ligand is observed with all the compounds investi gated affording [VO5L](-) and [VO(5)2L](-), respectively. Characterization of these species has been achieved by MSn experiments, which have allowed s pecific fragmentations of the peroxidic moiety to be distinguished. In part icular, with [VO(5)2L](-), two distinct modes of decomposition were observe d, depending on the presence in the ligand of a free carboxylic function. - Possible biochemical implications related to vanadium haloperoxidase enzym es are discussed.