Scopul nostru este sprijinirea şi promovarea cercetării ştiinţifice şi facilitarea comunicării între cercetătorii români din întreaga lume.
Autori: Simona Nica, Manfred Rudolph, Helmar Goerls, Winfried Plass
Editorial: Inorg. Chim. Acta, 360, p.1743-1752, 2007.
The hydrazone ligands derived from salicylaldehyde and aliphatic carbonic acid hydrazides react with equimolecular amounts of
ammonium metavanadate and 8-hydroxyquinoline in refluxing methanol to yield oxovanadium(V) complexes. The synthesis can alternatively
be performed starting from [VO(acac)2] followed by aerial oxidation to form the corresponding oxovanadium(V) complexes.
The molecular structures determined by X-ray crystallography feature in all cases a oxovanadium(V) moiety in an distorted octahedral
arrangement with an oxygen and nitrogen rich environment. The obtained compounds posses very good solubility in organic solvents,
permitting electrochemical investigation. Square wave voltammetric measurements revealed two reversible one-electron reduction steps
at 0.355 and – 1.638 V. The reduction of the oxovanadium(V) complexes to the corresponding vanadium(IV) species occurs at relatively
positive potential, which is independently verified by ESR spectroscopy. While the second reduction step appears to be accompanied by a
pre-wave exhibiting an unusual frequency dependence which can be attributed to ligand addition/elimination equilibria related to the 8-
hydroxyquinoline coligand. The oxovanadium(V) complexes can be converted into the corresponding cis-dioxovanadium(V) compounds
by reaction with aqueous NaOH. 51V NMR monitoring of this reaction reveals that one equivalent of base results in a full conversion
with the cis-dioxovanadium(V) complex being the only species present in solution.
Cuvinte cheie: Haloperoxidases, Oxovanadium complex, N-Salicylidene hydrazides, 8-Hydroxyquinoline, Crystal structure, Square wave voltammetry