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United States Department of Agriculture

Agricultural Research Service

Title: Redox and Catalytic Activity of Hemin in Ionic Liquids

Authors
item Compton, David
item Laszlo, Joseph

Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 30, 2001
Publication Date: N/A

Technical Abstract: Electrochemical and catalytic studies of hemin were performed in ionic liquids (IL) and N-methylimidazole (NMI)/IL mixtures. The cyclic voltammetry (CV) of hemin in 14% NMI solutions in 1-butyl- and 1-octyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6] and [omim][PF6]) resulted in a quasi-reversible electrochemical reduction. Using a Au working electrode referenced to Ag/AgCl at 50mV/s, the CV of hemin in 14% NMI/[bmim][PF6] resulted in a DeltaE1/2 = -300 mV. The relationship of ip vs. v1/2 for this redox event was linear. However, the DeltaE = 67 mV and ipr/ipo = 0.70 values indicate that the reduction of hemin is quasi-reversible in the NMI/IL mixtures. The reduction of hemin in 14% NMI/[omim][PF6] produced similar results with a DeltaE1/2 = -272 mV. Modifying the electrode surface with self-assembled monolayers (SAM) of 4,4'-dipyridyl disulfide (Aldrithiol-4, AT4) had little effect on the reduction of hemin in the NMI/IL solutions. The AT4-modification of the electrodes did not effect the DeltaE1/2 of the redox event but did increase the ipr and ipo of the redox signal slightly by 20 nA (ipr/ipo = 0.73). Efforts to study the redox properties of hemin:AT4-modified electrodes in 100% IL will also be presented. Also, the hemin-catalyzed oxidation of guaicol was studied in IL, and preliminary results indicate that hemin possesses peroxidase like activity.

Last Modified: 7/22/2014
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