Organometallic Charge Transfer and the Reduction of Carbon Dioxide

普渡大学化学系Clifford P. Kubiak博士受到化学系无机、生物无机和有机金属项目的支持，研究了在振动时间尺度上发生的有机金属系统中的电荷转移，这可以在马库斯- hush电子转移理论的框架内解释。羰基红外拉伸带的聚并证明了某些三钌团簇在振动时尺度附近发生价间电荷转移，这些配合物中电子交换速率的差异反映了配合物内部电子耦合的差异。在这个项目中，将描述控制这种耦合的因素。该现象的自洽物理描述将通过对三钌配合物的动态红外平均的详细光谱研究而得到发展。然后将通过对另外三种强耦合的有机金属电荷转移配合物的研究来概括这一图景：(i)横向相互连接的三核透明镍簇二聚体；（ii）具有强金属-金属相互作用的低聚金属簇；(3)新型四（二苯基膦）醌二甲烷桥接双核金属配合物。其中许多配合物具有适宜的氧化还原电位和催化性能，可用于二氧化碳的电化学还原，这方面的化学研究有待进一步发展。在许多化学反应中，反应物和生成物之间的电子转移是一个关键步骤。在这些过程中，电子转移的最大速率是由反应物和生成物分子内部的振动速率和溶剂运动速率决定的。这项研究解决了与分子振动速度相同的电子转移过程，并将确定控制电子转移速率的因素。这些结果将使人们对电子转移有一个更好的基本理解，并为设计具有调谐电子转移特性的系统提供基础。在项目中获得的基本知识的应用将通过设计能够化学激活二氧化碳的系统来展示。

Dr. Clifford P. Kubiak, Department of Chemistry, Purdue University, is supported by the Inorganic, Bioinorganic, and Organometallic Program of the Chemistry Division for an investigation of charge transfer in organometallic systems that occur on the vibrational time scale and that can be interpreted within the framework of the Marcus-Hush theories of electron transfer. Intervalence charge transfer occurs near the vibrational time scale in some triruthenium clusters, as evidenced by coalescence of carbonyl infrared stretching bands, and differences in the electron exchange rates in these complexes reflect differences in the electronic coupling within the complexes. In this project the factors that control this coupling will be delineated. A self consistent physical description of the phenomenon will be developed through detailed spectroscopic studies of the dynamical IR averaging in the triruthenium complexes. The picture then will be generalized by investigations of three additional, strongly coupled organometallic charge transfer complexes: (i) laterally interconnected dimers of trinuclear clear nickel clusters; (ii) oligomeric metal clusters with strong metal-metal interactions; and (iii) new tetra(diphenylphosphino) quinodimethane bridged dinuclear metal complexes. Many of these complexes have appropriate redox potentials and catalytic properties for the electrochemical reduction of carbon dioxide, and this aspect of their chemistry will be developed. The transfer of electrons between reactants and products is a critical step in many chemical reactions. In these processes the maximum rate of electron transfer is defined by the rate of vibrations within and solvent motions about the reactant and product molecules. This study addresses electron transfer processes that take place at the same speed as molecular vibrations and will determine the factors that control the electron transfer rate. The results will permit both a better basic understanding of electron transfer and provide a basis to design systems with tuned electron transfer properties. The application of the basic knowledge gained in the project will be demonstrated by devising systems that are capable of chemically activating carbon dioxide.