Photochemistry of Charge Transfer Excited States

这个奖项，从无机，生物无机和有机- 金属化学计划，是为了支持研究 两类双光子晶体激发态的光化学 一种络合物，其中的氘原子有六个d电子。 在 第一种情况，络合物将含有双齿二亚胺， 在激发态作为电子受体的配体 和作为电子供体的单齿配体， 激发态，它的电子是反应性的， 缺陷型。 这些分子的光化学激发 将产生配体-配体电荷转移（LLCT）激发 状态 本阶段调查的目标包括： 1)描述发生的光化学反应 通过LLCT产生的活性中间体的鉴别 激发，2）重排动力学的测定 和反应性基团的键断裂，以及3） 利用2）中获得的速率常数确定 结构和能量因素对寿命的影响 LLCT的激发态 在第二种情况下，sigma-to-pi 反键激发过程中的配合物， 含有双齿二亚胺和烷基配体的化合物。 在这里，激发态下的键断裂结果将 产生金属基和碳基自由基。 一个主要目标 这项工作的一个重要方面是将铝-碳键强度与 激发态键断裂速率。 %%% 光化学产生的激发态中的电荷转移是 生物光能收集的一个基本方面 系统. 电荷转移态如何充分 稳定在生物系统中， 比电荷复合发生得更快是一个谜， 继续激发令人兴奋的研究。 仿真成功 生物系统的发展可能意味着更有效地利用 技术用太阳能.第1部分： 系统中激发态的反应性，例如那些 在这一点上，这里的研究可能是有用的。 化学 正在研究的系统也可能是有用的， 用于聚合反应的活化催化剂。

This award, from the Inorganic, Bioinorganic and Organo- metallic Chemistry Program, is for the support of studies of the photochemistry of excited states of two types of rhenium complexes in which the rhenium atom has six d-electrons. In the first case the complex will contain a bidentate diimine ligand that serves as an electron acceptor in the excited state and a monodentate ligand that serves as an electron donor in the excited state, and which is reactive in its electron deficient form. Photochemical excitation of these molecules will generate a ligand-ligand charge transfer (LLCT) excited state. Objectives of this phase of the investigation include: 1) delineation of the photochemical reactions that occur andidentification of reactive intermediates produced via LLCT excitation, 2) determination of the kinetics of rearrangements and bond fragmentations of the reactive groups, and 3) utilization of the rate constants obtained in 2) to determine the effects of structural and energetic factors on the lifetime of the LLCT excited state. In the second case, sigma-to-pi antibonding excitation processes in rhenium(I) complexes that contain bidentate diimine and alkyl ligands will be examined. Here the results of bond scission in the excited state will produce metal- and carbon-based radicals. A primary objective of this work is to relate rhenium-carbon bond strength to the rate of excited state bond fragmentation. %%% Charge transfer in photochemically generated excited states is a fundamental aspect of biological light energy harvesting systems. How charge transfer states are sufficiently stabilized in biological systems so that productive reactions occur faster than charge recombination is a mystery that continues to stimulate exciting research. Successful emulation of biological systems could mean more efficient utilization of solar energy for technological purposes; determination of the reactivity of the excited state in systems such as those to be examined here may be useful in this regard. The chemical systems under study may also be useful as photochemically activated catalysts for polymerization reactions.