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，丹尼斯·埃文斯教授和他的团队将研究分子之间的相互作用以及分子在氧化和还原过程中的分子内结构重组。在联苯胺和联苯基体系中，将使用数字模拟方法和从独立的光谱实验获得的产物二聚常数来考察微弱的产物缔合对伏安信号的影响。这项工作可能导致对化学物种中的弱产物缔合进行前所未有的快速电化学检测，这些化学物种由于其不稳定的性质而无法进行光谱分析。探索将继续进行势反转，这是一种现象，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。这项工作将集中在一系列二芳胺和双芳基化合物，它们在第一次电子转移事件时经历了不同程度的内部结构重组。这项研究应该揭示潜在反转所必需的构造变化的程度。电化学结果将与通过电子顺磁共振(EPR)获得的均相歧化平衡常数进行比较。电活性分子内(内)重组能的独立测定将使用光电子能谱(PES)完成。这项研究将包括一些表现出潜在反转的物种。埃文斯小组将与华盛顿州立大学和太平洋西北国家实验室的王来生教授合作，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)的反应将特别令人感兴趣。将研究CEPT机理的要求，包括动力学势垒以及反应物和产物的酸碱性质。实验研究将与考虑溶剂介电屏蔽效应的pKa值的密度泛函理论计算(DFT/Cosmo)相补充。这项研究将加深对多电子转移反应的基本认识。将采用现代电化学方法。结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.