ELECTRON-TRANSFER BETWEEN AMPHIPHILIC FERROCENES AND ELECTRODES IN A BICONTINUOUS MICROEMULSION

Kinetics of electrochemical oxidations of ferrocene (Fc) and 2- and 5- (ferrocenylcarboxy)dodecyltrimethylammonium nitrates (2-Fc and 5-Fc, r espectively) were studied to yield information about the electrode-flu id interface in a bicontinuous microemulsion. Apparent standard hetero geneous electron-transfer rate constants (k degrees') for Fc, 2-Fc, an d 5-Fc at glassy carbon electrodes were similar in homogeneous acetoni trile, as found earlier in DMSO. In a bicontinuous microemulsion of n- tetradecane, water, pentanol, and cetyltrimethylammonium chloride (CTA C), electron-transfer rates for Fc, 2-Fc, and 5-Fc were an order of ma gnitude smaller than in acetonitrile. Ferrocene had a k degrees 'twice as large as 2-Fc and 5-Fc in the CTAC microemulsion. Small difference s in rates of 2-Fc and 5-Fc cannot be explained by a head down-tail up orientation at the time of electron transfer, as proposed to explain kinetics in micellar CTAB solutions. Results suggest the possibility o f increased disorder and mobility in the electrode-fluid interface in the CTAC microemulsion compared to micellar CTAB solutions.