Voltammetry - Linear sweep and cyclic, Second Edition

Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) are the most widely used voltammetric techniques for studying redox reactions of both organic and inorganic compounds because they are unmatched in their ability to provide information on the steps involved in electrochemical processes with only a modest expenditure of time and effort in the acquisition and interpretation of data. These electroanalytical methods require simple and inexpensive instrumentation and provide not only information on the electrochemical quantities typical of a redox process, but also allow investigations of chemical reactions coupled with charge transfer steps. This is because the electrode can be used as a tool for producing reactive species in a small solution layer surrounding its surface and at the same time to monitor chemical reactions involving these species. Moreover, since the relevant responses can be obtained within a few milliseconds after stimulation of the electrode, they may be used for studying mechanisms involving very fast reactions, thus allowing detection of short-lived transient intermediates. LSV and CV techniques were proposed at the beginning of the 1950s and in those years some theoretical approaches able to rationalize the simplest responses were worked out. However, the use of these electroanalytical methods has received considerable impetus only more recently thanks to increased knowledge of more subtle criteria for interpreting the relevant responses and to greater availability of theoretical tools for processing experimental data. This article will briefly survey the analytical performance of these techniques, as well as the criteria followed to gain information regarding participants in electrochemical processes from the recorded responses

The solution state of nickel(II) and nickel(I) in the presence of diphosphines in acetonitrile. A combined electroanalytical and spectrophotometric approach

The equilibria involving nickel(II), nickel(I) and nickel(0) in the presence of bidentate phosphine ligands in acetonitrile solution have been investigated by cyclic voltammetry, controlled-potential electrolysis, and spectrophotometry. The obtained results show that when both cone angles and PP distance make the diphosphine well-suited to act as a chelating ligand, only bis-chelate complexes of the type NiL2 are formed by nickel in all the three achieved oxidation states. Longer methylene chains interposed between the phosphorus atoms make the diphosphine less suited to act in a bidentate fashion, thus allowing lower-order complexes, e.g. NiLS2 (S = solvent), to be obtained for nickel in the +2 and +1 oxidation states. Evidence for the poor stability of the [NiILS2]+ complexes and for a higher-order complex of the type NiL3 for nickel(II) have also been obtained. The dependence of the reduction potentials on the nature of the diphosphine employed is discussed. © 1984