TIME RESOLVED INFRARED STUDIES OF ELECTRON TRANSFER COUPLED NUCLEAR ORGANIZATION

电子转移(ET)是自然界最重要的反应之一， 在呼吸和光合作用途径中发挥关键作用 基本的生物能量学意义。虽然相对较好地理解 作为一个反应类，ET反应并没有详细地理解为 定义反应性的分子特征：超快振动 光谱学(红外或相干光学)将提供第一个直接 实验探测器将有助于破译分子运动是如何 与实际的外星人事件相结合。 重组能量(L)，由内球体(高频)组成 施主、受主和介质的振动模)和外球 (溶剂或镀液的低频振动模)贡献，是 在确定ET在给定的时间内发生的速度方面具有主要意义 供体-受体系统。我们的目标是实际识别和测量 振动模式的能量是ET反应坐标的关键 代表着一个未被探索的实验前沿：有可能增加 我们对电荷转移化学的基础知识以及 影响已开发的用于描述ET的理论框架 反应是巨大的。 我们的工作集中在简单的供体-受体复合体上，这些复合体经历了快速 电荷分离和/或改变复合反应(Ket大于 2 x 10[12]S-1)；FAST ET的要求确保了振动 激发态反应物以及基态和激发态的脱相 ET产品不会出现在我们的实验时间范围内。模型系统 其允许对反应中心型发色团进行成对检查 (如卟啉和苯二酚)在这项提案中占突出地位。 类似于重组能和反应的紧密耦合 自由能，人们相信激活的振动模式 光合作用反应中ET和接受能量的生色团 中心在高效分离客户资源方面发挥着核心作用 在早期的光合作用过程中，穿过膜的孔中的电子。 到目前为止，已完成的工作主要集中在利用光抽运相干 用光学探头实验研究发生得比 溶剂的纵向弛豫时间。这样一个连贯控制的 ET反应最近被认为与长程光合作用有关 电荷分离事件。除了我们设计的实验成果之外 发展对ET中连贯现象的基本认识 反应，其他工作利用光泵-IR探测器实验来探测 容易识别的高频和低频之间的关系 生色团振动光谱标签(C-O和C-N伸缩模式， 芳烃和吡啶环呼吸模式、卟啉褶皱模式等) 和ET反应的坐标。如此详细的研究如何分子 振动耦合到ET将两者都提供一个新的水平 对生物电荷分离反应的理解和帮助 模仿光合作用的人工系统的设计，潜在地 影响新的能源储存技术。

Electron transfer (ET) is one of Nature's most important reactions, playing key roles in respiratory and photosynthetic pathways that are of fundamental bioenergetic significance. Though relatively well understood as a reaction class, ET reactions are not understood in detail in terms of the molecular features that define reactivity: ultrafast vibrational spectroscopy (infrared or coherent optical) will provide the first direct experimental probe that will help decipher how molecular motions are coupled to actual ET events. The reorganization energy (l),comprised of inner-sphere (high-frequency vibrational modes of the donor, acceptor, and medium) and outer-sphere (low-frequency vibrational modes of the solvent or bath) contributions, is of primary significance in determining how fast ET occurs in a given donor-acceptor system. Our goal to actually identify and measure the energy of vibrational modes that are key to an ET reaction coordinate represents an unexplored experimental frontier: the potential to add to our fundamental knowledge of charge transfer chemistry as well as influence the theoretical framework that has been developed to describe ET reactions is enormous. Our work focuses on simple donor-acceptor complexes that undergo fast charge separation and/or change recombination reactions (kET greater than 2 x 10[12] s-1); the requirement of fast ET ensures that vibrational dephasing of excited-state reactants as well as ground- and excited-state ET products does not occur on our experimental timescale. Model systems that allow pair-wise examination of reaction center-type chromophores (such as porphyrins and quinones) feature prominently in this proposal. Similar to the intimate coupling of reorganization energy and reaction free energy, it is believed that the vibrational modes that activate chromophores for ET and accept energy in the photosynthetic reaction center play a central role in the highly efficient separation of an electron from a hole across a membrane during early photosynthetic events. Work completed to date has concentrated on utilizing optical pump-coherent optical probe experiments to study ET reactions that occur faster than the longitudinal relaxation time of the solvent. Such a coherently controlled ET reaction has recently been implicated in the long-range photosynthetic charge separation event. In addition to our experimental efforts designed to develop a fundamental understanding of coherence phenomena in ET reactions, other work exploits optical pump-IR probe experiments to probe the relationship between the readily identifiable high and low frequency chromophore vibrational spectroscopic tags (C-O and C-N stretching modes, arene and pyridinium ring breathing modes, porphyrin ruffling modes, etc.) and the ET reaction coordinate. Such detailed studies of how molecular vibrations are coupled to ET will both provide a new level of understanding of biological charge separation reactions as well as aid in the design of artificial systems that mimic photosynthesis, potentially impacting new energy storage technologies.