This article was downloaded by: [Abd El-Motaleb Ramadan]
On: 23 September 2011, At: 23:11
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
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Synthesis, Characterization, and Tyrosinase Biomimetic Catalytic Activity of
Copper(II) Complexes with Schiff Base Ligands Derived from α- diketones with
2-methyl-3-amino-(3H)-quinazolin-4-one
Abd El-Motaleb M. Ramadan a , Shaban Y. Shaban a & Mohamed M.
Ibrahim a
a Chemistry Department, Faculty of Science, Kafr El-Sheikh
University, Kafr El-Sheikh 33516, Egypt
Available online: 23 Sep 2011
ABSTRACT
A template condensation of α-diketones (biacetyl, benzile and 2,3-pentanedione) with 2methyl-3-amino-(3H)-quinazolin-4-one (AMQ) in the presence of CuX2 (X = Cl-, Br-, NO3- or
ClO4-) resulted in the formation of tetradentate Schiff base copper(II) complexes of the type
[CuLX]X and [CuL]X2. Structural characterization of the complex species was achieved by
several physicochemical methods, namely elemental analysis, electronic spectra, ir, esr, molar
conductivity, thermal analysis (TAG & DTG), and magnetic moment measurements. The
stereochemistry, the nature of the metal chelates, and the catalytic reactivity are markedly
dependent upon the type of counter anions and the ligand substituent within the carbonyl
moiety. A square planar monomeric structure is proposed for the perchlorate, nitrate, and
bromide complexes, in which the counter anions are loosely bonded to copper(II) ion. For the
chloride complexes, the molar conductivities and the spectral data indicated that they have
either square planar or square-pyramidal environments around copper(II) center. The reported
copper(II) complexes exhibit promising tyrosinase catalytic activity towards the
hydroxylation of phenol followed by the aerobic oxidation of the resulting catechol. A linear
correlation almost exists between the catalytic reactivity and the Lewis-acidity of the central
copper(II) ion created by the donating properties of the parent ligand. The steric
considerations could be accounted to clarify the difference in the catalytic activity of these
functional models.