Catalytic Activity of Histidine-Metal Complexes in Oxidation Reactions

Abstract

Studies were carried out to determine the activity of complexes of essential amino acid histidine with heavy metals in the oxidation of cyclohexene with tert-butylhydroperoxide in toluene at 80°C. All complexes were prepared by interaction of metal ions and histidine at room temperature in aqueous solutions. Only the complexes of Mo and W were obtained from acidic aqueous solution. These complexes were characterized by UV-vis, FT-IR, Mössbauer spectroscopy, and EPR analysis. The products of the oxidation reactions were identified by GC/MS analysis. The complexes of Mo and V showed the best activity in the epoxidation reaction of cyclohexene in comparison with other complexes, such as Ni, Mn, Zn, Co, Cu, Cr, Fe, and W. The probable structures of the complexes are propounded on the basis of the analyses carried out.

Keywords:

• catalysis
• histidine
• metal complexes
• oxidation
• properties
• structure

Acknowledgments

The authors would like to thank Prof. DSc I. Mitov and Dr. D. Paneva from the Institute of Catalysis, Bulgarian Academy of Sciences, for the many useful discussions of Mössbauer spectra.