US EPA

1446742 

Journal Article 

Synthesis, characterization, magnetic, thermal and electrochemical studies of oxidovanadium (IV) picolyl hydrazones as functional catechol oxidase models 

El-Taras, AA; El-Mehasseb, IM; Ramadan, A 

2012 

Yes 

Academie des Sciences. Comptes Rendus. Chimie
ISSN: 1631-0748 

15 

4 

298-310 

10.1016/j.crci.2011.11.009 

WOS:000305547900006 

The picolyl hydrazone ligands derived from picolonic acid
hydrazide and alpha-pyridyle ketone (L-1, L-2 and L-3), alpha-acetyl thiophene (L-4), alpha-
formyl or alpha-acetyl phenol (L-5 and L-6 respectively) and 2-hydroxy-1-naphthaldehyde (L-7)
react with equimolecular amount of vanadyl sulfate in refluxing methanol to yield oxidovanadium
(IV) complexes. The structure of the obtained ligands and their oxidovanadium (IV) complexes were
characterized by various physicochemical techniques, viz, elemental analysis, molar conductance,
magnetic susceptibility measurements, thermal analysis (TGA & DTG), IR, electronic absorption and
ESR spectral studies. Cyclic voltammeteric behavior of the complexes has also been discussed.
Five-coordinate square-pyramidal structure was proposed for all complexes. A monomeric nature was
reported for complexes (2),(3), (6), and (7), while dimeric structures were suggested for
complexes (1), (4) and (5). The ability of the complexes to catalyze the aerobic oxidation of
catechol to the light absorbing o-quinone has been investigated. The results obtained show that
all complexes catalyze this oxidation reaction and large variations in the rate were observed.
Electrochemical data for most complexes show that there is a linear relationship between their
ability to oxidize catechole and their E-1/2 potentials. The most effective catalysts were those
complexes which exhibited E-1/2 values approached to the E degrees value of the natural
tyrosinase enzyme isolated from mushroom, while those that largely deviated from that potential
exhibited lower oxidase catalytic activity. The probable mechanistic implications of the
catalytic oxidation reactions are discussed. (c) 2011 Academie des sciences. Published by
Elsevier Masson SAS. All rights reservedI 

Synthesis; Characterization; Magnetic; Thermal; Oxidovanadium (IV); Hydrazones; Catechol oxidase models