Thermodynamics for complex of L-histidine with molybdenum (VI) Model Anticancer Drugs

Document Type: Research Paper

Abstract

Organometallic complexes offer potential for design as anticancer drugs. A quantitative
model that discriminates anticancer compounds from the inactive ones in a training series was
Equilibrium of the reaction of molybdenum (VI) with l-histidine have been studied
in aqueous solutions at pH range of 4-8, using spectrophotometry and optical rotation
methods at constant ionic strength of 0.15 mol.lit-1 of sodium perchlorate at c 0 25  0.1 .
L-histidine has been proposed to be present at the active site of a number of enzymes. In
addition, as a part of cytochrome-c, it is apparently involved in the electron transport systems.
Also, molybdenum (VI) is an essential component of several enzymes which catalyze
reactions. In this project, we have determined the pH in which the complex is formed using
spectrophotometry and polarimetry techniques. The molar ratio of metal to ligand in a
molecule of complex was 1:1, and the stability constant of this complexation process has been
determined by polarimetry and spectrophotometry methods at different wavelengths. The
stability constant decreases upon increasing the pH over 6, so the stability constant of
complex of Mo (VI) with l-histidine has been determined at pH=5.8. We have used literature
to propose a structure for the complex molecules. So the proposed structure is an octahedral
with a central core consists of MoO3 with three binding sites for complexation. Thus, histidine
as tridentate ligand can made a chelate with the metal, through the oxygen of carboxylic
group, the nitrogen of amides group and the charged nitrogen of imidazole ring donors.

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