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United States Department of Agriculture

Agricultural Research Service

Title: Bioelectrocatalytic Reactions in Room Temperature Ionic Liquids

Authors
item Compton, David
item Laszlo, Joseph

Submitted to: International Symposium on Molten Salts
Publication Type: Proceedings
Publication Acceptance Date: May 17, 2002
Publication Date: N/A

Interpretive Summary: Ionic liquids are a new, nonvolatile, environmentally friendly class of solvents than can be substituted for volatile organic solvents. One of our goals is to invent methods of transforming agricultural products to higher value products that use ionic liquids instead of more common organic solvents. This study examines the use of electrodes in ionic liquids to activate molecules containing iron atoms. These results provide preliminary evidence that iron-containing enzymes can be activated by electricity in ionic liquids to carry out a variety of reactions to make agriculturally based cosmetics, skin care products, and nutrition supplements. The fact that the iron-containing enzymes can be used several times in the environmentally friendly ionic liquids results in less waste and a "greener" method of producing the desired products.

Technical Abstract: The direct electrochemical reduction of hemin, protopophyrin(IX) iron(III) chloride, ligated with strong or weak heterocyclic bases, was investigated in the ionic liquids (ILs), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([omim][PF6]), using cyclic voltammetry and chronocoulometry. E1/2 values of hemin complexed with N-methylimidazole (NMI) or with pyridine (without electrolyte) were determined in the ILs (without electrolyte) and in methanol (1.0 M electrolyte). The diffusion coefficients and heterogeneous electron-transfer rate constants of hemin in the ILs were also determined. Cyclic voltammetry of hemin adsorbed to a gold surface through 4,4'-bispyridyl disulfide linkages showed a large positive shift in the oxidation wave. The surface concentration of the adsorbed hemin was resolved. Our findings suggest that while hemin is electrochemically active in ILs, its behavior is modified by ligand field strength and surface adsorption phenomena.

Last Modified: 7/31/2014
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