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

Organometallic complexes offer potential for design as anticancer drugs. A quantitativemodel that discriminates anticancer compounds from the inactive ones in a training series wasEquilibrium of the reaction of molybdenum (VI) with l-histidine have been studiedin aqueous solutions at pH range of 4-8, using spectrophotometry and optical rotationmethods 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. Inaddition, 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 catalyzereactions. In this project, we have determined the pH in which the complex is formed usingspectrophotometry and polarimetry techniques. The molar ratio of metal to ligand in amolecule of complex was 1:1, and the stability constant of this complexation process has beendetermined by polarimetry and spectrophotometry methods at different wavelengths. Thestability constant decreases upon increasing the pH over 6, so the stability constant ofcomplex of Mo (VI) with l-histidine has been determined at pH=5.8. We have used literatureto propose a structure for the complex molecules. So the proposed structure is an octahedralwith a central core consists of MoO3 with three binding sites for complexation. Thus, histidineas tridentate ligand can made a chelate with the metal, through the oxygen of carboxylicgroup, the nitrogen of amides group and the charged nitrogen of imidazole ring donors.