Analytical and Mechanistic Studies in Electrochemistry

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In this research supported by the Analytical and Surface Chemistry Program, Professor Dennis Evans and his group will examine intermolecular interactions and intra-molecular structural reorganization of molecules as they undergo oxidation and reduction. Weak product association effects on voltammetric signals will be examined in benzidine and biphenylene based systems using digital simulation methods and product dimerization constants obtained from independent spectroscopic experiments. This work may lead to unprecedented fast electrochemical detection of weak product associations in chemical species that are not amenable to spectroscopic analysis because of their unstable nature. Exploration will continue on potential inversion, the phenomenon where the insertion or removal of the second electron in a two electron process occurs more easily than does removal of the first electron. This work will focus on a series of dianisidine and bi-aryl compounds which undergo varying degrees of internal structural reorganization upon the first electron transfer event. This study should reveal the extent of structural change that is necessary for potential inversion. Electrochemical results will be compared with homogenous disproportionation equilibrium constants obtained via electron paramagnetic resonance (EPR). Independent determination of the inner (internal) reorganization energies of electroactive molecules will be done using photoelectron spectroscopy (PES). This study will include some species which exhibit potential inversion. The Evans group will collaborate with Professor Lai-Sheng Wang of Washington State University and the Pacific Northwest National Laboratory to determine inner reorganization energies of anion species using PES and electrospray ionization. Reactions that involve concerted electron and proton transfer (CEPT) will be of special interest. Requirements for the CEPT mechanism including kinetic barriers and the acid-base properties of reactants and products will be investigated. Experimental studies will be complimented with density functional theory calculations (DFT/COSMO) of pKa-values, which take into account solvent dielectric screening effects. This research will develop fundamental understanding of multi-electron-transfer reactions. Modern electrochemical methodology will be employed. Outcomes will be highly relevant to a wide range of areas. Processes that affect biological systems, energy production, and synthesis of high value chemicals are a few examples.