Spectroscopic and Electrochemical Studies on Cobaloximes and Alkylcobaloximes in Aqueous Surfactant Micelles as Models of Vitamin B 12

Abstract

Various synthetic models of VitaminB 12 are prepared using dimethylglyoxime, pyridine, imidazole and methyliodide as ligands and their spectroscopic and electrochemical results are compared with the natural analogues methylcobalamin and cyanocobalamin. The spectroscopic and electrochemical results of these compounds are studied in hydrophobic membrane mimicking systems such as aqueous systems of Sodium dodecyl sulfate (SDS), Cetyl trimethyl ammonium bromide (CTAB). The hydrophobic environment of aqueous surfactant micellar solutions around the metal complexes at the active site of the metalloproteins under physiological pH has considerable effect on the electronic spectrum of the model compounds. Platinum working electrode gives a more reliable result for vitamin B 12 showing a reversible couple in the range from -0.3 to -0.6 V. Cobaloxime complexes show reversible couple in the range from -0.6 to -0.8 V with glassy carbon electrode whereas methylcobalamin shows positive redox potential values with glassy carbon electrode. Micellar systems stabilize the organometallic derivatives in aqueous solutions.