John K. Foley

Electrolyte effects on the cyclic voltammetry of TCNQ and TCNE

Abstract The reductions of TCNQ and TCNE to their anion radicals and dianions at platinum and carbon electrodes in acetonitrile solution have been studied by cyclic voltammetry, using a variety of supporting electrolytes. At sweep rates up to 500 mV s−1 the first reduction waves of both TCNQ and TCNE are reversible, with half-wave potentials independent of supporting electrolyte and electrode material. The half-wave potentials of the second reduction waves, however, are less negative in the presence of LiClO4 or NaClO4 than in the presence of TBAF or TEAP. This is attributed to ion pairing between the dianions and the alkali metal cations. The second reduction wave of TCNQ is reversible up to 500 mV s−1 but the electrode kinetics of the second wave of TCNE are dependent upon electrolyte and electrode material, probably because of variations in the metal-outer Helmholz plane distance or non-adiabaticity.

Homogeneous reaction involving components of different redox couples—I. theoretical considerations and digital simulation

Abstract : Coupled heterogeneous electron transfer/homogeneous reactions occur in the electro-oxidation of certain anilines, and in association reactions of hydrocarbon anions with metal cations. If the adduct A sub m sub R is electroinactive, the resulting voltammogram is distorted in a way which is characteristic of the value of m. The derivation of the theoretical fluxes for these reactions and calculated normal potential pulse voltammograms are presented. The results are derived from both limiting flux and digital simulation considerations. (Author)

Homogeneous reaction involving components of different redox couples—II. polarographic studies of the interactions of alkali metal cations with athracene and fluoranthene dianions in N,N-dimethylformamide and acetonitrile

Abstract The polarographic behavior of mixtures of anthracene (An), fluoranthene (Fa) and alkali metal cations in N,N -dimethylformamide (DMF) or acetonitrile (ACN) indicates that the electrogenerated dianion of the hydrocarbon reacts with the metal cation in the diffusion layer to form ion complexes. This results, in the case of sodium or lithium cations with anthracene in both DMF and ACN, in the appearance of inverted polarographic waves. In the case of other alkali metal cations (K + , Rb + ), the intensity of the polarographic wave due to the reduction to the hydrocarbon dianion is simply decreased. The stoichiometries and mechanisms of the interactions are discussed. In the presence of proton donors such as water, a competing reaction for the dianion results. The polarograms are simulated by digital approximation techniques.

Interfacial Infrared Vibrational Spectroscopy

The last five years have been to electrochemical infrared spectroscopy what the 1940s were to standard infrared spectroscopy. Prior to World War II, Raman spectroscopy was the most commonly used form of vibrational spectroscopy. The development of infrared technology, particularly detector technology, during World War II led to the rapid growth of infrared spectroscopy. In part owing to the relative cost advantage, the use of infrared spectroscopy rapidly overtook Raman spectroscopy for routine vibrational analyses. The advent of the laser produced a resurgence in Raman spectroscopy but it still ranks far behind infrared spectroscopy in routine use. We are today on the verge of a period in which rapid growth in electrochemical infrared spectroscopy can be expected. Furthermore, as will be discussed below, infrared methods may have greater sensitivity and versatility as a general spectroscopic probe for electrochemical systems than Raman methods. The recent development of electrochemical infrared spectroscopy resulted not from technological breakthroughs but from the marriage of well-established electrochemical and spectroscopic techniques.