Electric Field Effects on Excited State and Electron Transfer Dynamics

斯坦福大学的Boxer教授将在无机、生物无机和有机金属化学项目的支持下，使用Stark效应光谱学来研究简单分子中的电荷转移过程。该技术需要将样品（包含感兴趣的分子的薄膜）置于高且可变的电场中，并观察电场对光的吸收或发射的影响。所获得的特征线形可提供有关跃迁偶极子与分子轴之间关系的信息。要研究的过程包括LMCT跃迁、分子内电子转移反应、质子转移反应和振动跃迁。特别令人感兴趣的是驱动力对电子转移速率的影响。待研究的分子包括配位配合物，如三（联吡啶基）钌（II）离子和相关的混价物质、共价连接的二苯酮/萘衍生物、卟啉/醌类、某些铼配合物和溴苯。这项新技术将为分子动力学的认识增加一个重要的新维度。一个特别棘手的问题是如何理解分子内电荷的流动。例如，如果一个分子吸收了可见光的光子，分子内的电子在空间上是如何反应的？鲍克瑟教授开发了一种潜在的强大的新技术，称为斯塔克效应光谱学，来回答这些问题。从本质上讲，当分子与光的相互作用被测量时，它们受到高电场的影响。即将获得的结果将揭示分子的不同部分是如何“交流”的，并将提高对光合作用和相关现象中非常重要的电荷分离过程的理解。

Professor Boxer of Stanford University will use Stark effect spectroscopy to investigate charge-transfer processes in simple molecules, with support from the Inorganic, Bioinorganic, and Organometallic Chemistry Program. The technique entails subjecting the sample (a thin film containing the molecule of interest) to a high and variable electric field, and observing the effect of the field on the absorption or emission of light. Characteristic lineshapes are obtained that yield information regarding the relationship between the transition dipole and the molecular axes. Processes to be investigated include LMCT transitions, intramolecular electron transfer reactions, proton transfer reactions, and vibrational transitions. Of particular interest is the influence of driving force on electron transfer rates. Molecules to be investigated include coordination complexes such as tris(bipyradyl)ruthenium(II) ion and related mixed-valence species, covalently-linked benzophenone/naphthalene derivatives, porphyrin/quinone species, certain rhenium complexes, and bromobenzene. This new technique should add an important new dimension in the understanding of molecular dynamics. %%% A particularly nettlesome problem is to understand the flow of charge within molecules. For example, if a molecule absorbs a photon of visible light, how do the electrons within the molecule respond spatially? Professor Boxer has developed a potentially powerful new technique, called Stark effect spectroscopy, to answer such questions. Essentially, the molecules are subjected to high electric fields while their interactions with light are measured. The results to be obtained will reveal how different parts of a molecule "communicate" and will improve understanding of the charge-separation processes so important in photosynthesis and related phenomena.