The Chemistry of Two-Electron Mixed Valence Excited States

这个奖项在无机，生物无机和有机化学计划支持研究的两个电子转移反应的博士丹尼尔G。Nocera，马萨诸塞州理工学院化学系。 研究的目的是阐明激发态的反应途径发生在两个电子步骤的光活化金属中心的氧化还原反应。 研究的每个络合物将包含两个不同氧化态的金属原子，通过单个或多个金属-金属键连接。 在单个金属-金属键合物质的情况下，金属的氧化态相差两个。 例如，光消除的二氢或二卤素从二铑的二氟膦配体桥接的二卤代卤化物预计进行通过Rh 2（II，0）的混合价中间体，可以表征。 其他配合物，包括含有不对称配体，以稳定两个电子的混合价中心，将合成和研究。 在通过多重键连接的二聚体的情况下，将通过光生具有M-M+特征的核来实现双电子混合价态。 这些物质可以从具有四重键或具有共享边的双八面体排列的络合物中获得。 本课程将探讨各种基材的光引发键加成和原子转移反应。多电子反应尚未被充分理解，但在许多重要的过程中都会发生，包括电子转移、能量转换和信息处理。 这里研究的反应是不寻常的，因为一个光子促进两个电子的运动。 了解多电子转移的机制，应该开辟新的反应，涉及过渡金属和小分子光转化的方式。 参与该项目的学生将体验合成技术和物理方法。

This award in the Inorganic, Bioinorganic, and Organometallic Chemistry Program supports research on two-electron transfer reactions by Dr. Daniel G. Nocera of the Chemistry Department, Massachusetts Institute of Technology. The goal of the research is to elucidate excited state reaction pathways for oxidation-reduction reactions occurring in two-electron steps at photoactivated metal centers. Each complex studied will contain two metal atoms in different oxidation states, linked by either single or multiple metal-metal bonds. In the case of single metal-metal bonded species, the oxidation states of the metals differ by two. For example, photoelimination of dihydrogen or dihalogen from hydrido halides of dirhodium bridged by difluorophospine ligands is expected to proceed through a Rh2(II,0) mixed valence intermediate that can be characterized. Additional complexes, including ones containing asymmetric ligands to stabilize the two-electron mixed valence centers, will be synthesized and studied. In the case of dimers linked by multiple bonds, two-electron mixed valency will be achieved by photogenerating a core with M-M+ character. Such species can be obtained from complexes with quadruple bonds or with an edge-sharing bioctahedral arrangement. Photoinitiated bond addition and atom transfer reactions for a variety of substrates will be explored.Multielectron reactions are not well understood, but occur in many important processes, including photocatalysis, energy conversion, and information processing. The reactions studied here are unusual in that one photon promotes the movement of two-electrons. Understanding the mechanism of multielectron transfer should open the way to new reactions involving transition metals and small molecule phototransformations. Students involved in the project will experience both synthetic techniques and physical methods.