Enantioselective Redox Transformations at Electrodes Modified with Cholesteric Liquid Crystals

摘要

The electrochemical response of the resolved forms of tris (2,2'-bipyridyl) ruthenium (II/III) was examined at electrodes modified with a cholesteric liquid crystal. Films of cholesteryl oleyl carbonate were cast from solutions in a variety of solvents onto glassy carbon or platinum electrodes by spraying with an air-brush, by spin-coating, and by dropping from a micro syringe. At times, polyvinyl pyridine was incorporated to increase the viscosity of the film. Cyclic voltammetry was performed in water and acetonitrile. In the case of the aqueous electrolyte, both achiral and chiral salts were employed to assess their effect. The best results are demonstrated for the films which were sprayed on and subsequently examined using aqueous achiral electrolytes. The ratio for discrimination of one enantiomer vs. the other is 0.78. Films were also characterized microscopically before and after the electrochemical experiment. In a preliminary fashion, effects of the temperature and of the potential perturbation profile (triangular, square and sine) were explored.