Analytical and Mechanistic Studies in Electrochemistry

在这项由分析和表面化学计划支持的研究中，Dennis Evans教授和他的团队将研究分子在氧化和还原过程中的分子间相互作用和分子内结构重组。弱产物缔合效应对伏安信号将检查在联苯胺和联苯为基础的系统使用数字模拟方法和产品二聚化常数从独立的光谱实验获得。这项工作可能会导致对化学物质中弱产物关联的前所未有的快速电化学检测，这些化学物质由于其不稳定的性质而无法进行光谱分析。对势反转的探索将继续进行，势反转是指在双电子过程中第二个电子的插入或移除比第一个电子的移除更容易发生的现象。本工作将重点研究一系列在第一次电子转移事件中发生不同程度内部结构重组的二苯胺和双芳基化合物。这项研究应该揭示构造变化的程度，这是潜在反转所必需的。电化学结果将与通过电子顺磁共振（EPR）得到的均匀歧化平衡常数进行比较。利用光电子能谱（PES）独立测定电活性分子的内部（内部）重组能。这项研究将包括一些表现出潜在反转的物种。Evans小组将与华盛顿州立大学的王来生教授和西北太平洋国家实验室合作，利用PES和电喷雾电离来确定阴离子物种的内部重组能。涉及协同电子和质子转移（CEPT）的反应将特别有趣。对CEPT机制的要求，包括动力学障碍和反应物和产物的酸碱性质将进行研究。实验研究将辅以pka值的密度泛函理论计算（DFT/COSMO），其中考虑了溶剂介电筛选效应。本研究将发展对多电子转移反应的基本认识。将采用现代电化学方法。成果将与广泛的领域高度相关。影响生物系统、能源生产和高价值化学品合成的过程就是几个例子。

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.