A BINDING ISOTHERM BETWEEN FERROCENE MEDIATORS AND GLUCOSE OXIDASE FOR USE IN BIOANODE DEVELOPMENT AND INITIAL STUDIES OF AN ELECTROCATALYTIC DEOXYDEHYDRATION REACTION

Abstract

Enzymatic bioelectrodes are powered by renewable biomass sources. Glucose-powered bioelectrodes are prepared from ferrocene-functionalized linear poly(ethylenimine) (Fc-LPEI) cross-linked with ethylene glycol diglycidyl ether (EGDGE). Glucose bioanodes are normally only powered by the oxidation of glucose, however it can be envisioned that the bioanode could be used to power an electrochemical reduction. In considering a disproportionation-like system, a reaction that reduces glucose could be powered by an anodic oxidation of glucose. A potential candidate for the electrochemical reduction is deoxydehydration (DODH), as glucose contains vicinal hydroxyl groups. In this work, a Langmuir binding isotherm was detected electrochemically using cyclic voltammetry when Glucose Oxidase is treated as an inhibitor for (ferrocenylmethyl)trimethylammonium chloride (FcTAMCl) oxidation/reduction. A binding constant, Ka, was calculated from cyclic voltammetric data. This binding isotherm was observed in other ferrocene molecules, including ferrocencarboxylic acid, (((methoxy)ethoxy)ethoxy)methylferrocene, and bis(trimethylammoniummethyl)ferrocene, and were on the magnitude of 2.0 x 106 through 6.4 x 107. The magnitude of the binding isotherm varies between each derivative, with the glycol ether derivative exhibiting the strongest isotherm. Based on this Ka, a new glycol ether containing ferrocene-functionalized LPEI (FcG2LPEI) was prepared. The amperometric performance of this new material in the presence of 100 mM glucose is compared against similarly substituted ferrocenymethyl-functionalized LPEI (FcC1LPEI) that was developed by the Glatzhofer group. The amperometric performance of the FcG2LPEI is better than the amperometric performance of the FcC1LPEI, suggesting that this binding isotherm may be indicative of potential mediator performance in the polymer-supported state. Rhenium-based deoxydehydration catalysts were prepared and are demonstrated to be effective DODH catalysts for vicinal diols, using a variety of molecular and elemental reductants. The electrochemical behavior of (Me3TACN)ReO3PF6 wa investigated in aprotic media in the absence and presence of a variety of acids. The strength of the acid appears to affect the reduction potential of the complex. Attempts to prepare the Re(V) glycolate made from ReOCCl3(PPh3)2, Me3TACN, and styrene glycol were successful in deuterated dichloromethane, but not successful in deuterated acetonitrile. Attempts to prepare the Re(V) glycolate using bulk electrolysis were not successful.