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

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 obtained 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 at25  0.10c . 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.