CHEMICAL MODELS FOR BIOLOGICAL ELECTRON TRANSFER

许多生物过程严重依赖于电子。 转移：氧化磷酸化、光合作用和氧化还原 金属酶的反应仅举几例。如果一个基本的 对这些系统的理解是要实现的，它们的非凡之处 必须解释效率和选择性。距离的距离 氧化还原位之间的分离和 电子转移反应被认为在 控制电子转移的速度。这份提案提出了 一项广泛的研究计划，旨在探索 距离和驱动力对热电子速率的影响 金属之间的转移。为此，一系列双核金属 将在桥联配体所在的位置制备络合物 严格保持这两种金属的饱和结构 距离以及该距离可以系统地 多种多样。此外，这些建筑群的设计使 这两种金属的还原电位的差异是已知的， 也可以更改。有两种常见的方法 呈上了。(A)在第一系统中，一系列RU2和OS2 联吡啶配合物将被用来间接探测 用物理方法研究电子转移的机理 性质(价间电荷转移跃迁， 比例常数，以及电子离域和 混合价(M-M+)态的耦合)。(B)在第二次 接近，一系列的Ru-Os联吡啶配合物将被 用来直接测量电子转移速率 以探索距离对速度的影响。 固定电势。此外，通过改变表面上的取代基， 结合在每种金属上的联吡啶配体，其还原电位 为了研究(1)影响，将改变两个金属位置 氧化还原不对称性对混合价态性质的影响 以及(2)确定作为以下函数的电子转移速率 恒定距离的驱动力。已经有无数次 距离和驾驶影响的理论处理 力对混合价络合物物理性质的影响 关于电子转移的速度。通过此方法获得的数据 总体方法将提供几个严格的实验测试 这些理论中。只有通过系统的调查才能做到 结构定义的双核金属络合物，由非-桥联 共轭配体，将出现准确的图像 距离和驱动力在决定 混合价态的性质与电子率 金属之间的转移。

A number of biological processes depend critically upon electron transfer: oxidative phosphorylation, photosynthesis and the redox reactions of metalloenzymes to name just a few. If a basic understanding of such systems is to be achieved, their remarkable efficiency and selectivity must be explained. The distance of separation between redox sites and the driving force of the electron transfer reaction are thought to play crucial roles in controlling the rate of electron transfer. This proposal presents an extensive program of research designed to probe the effects of distance and driving force on the rates of thermal electron transfer between metals. To that end, a series of binuclear metal complexes will be prepared where the bridging ligands are saturated structures that rigidly hold the two metals a defined distance apart and where that distance can be systematically varied. In addition, the complexes have been designed so that the difference in reduction potentials of the two metals is known and can also be changed. Two general approaches have been presented. (A) In the first system, a series of Ru2 and Os2 bipyridyl complexes will be used to indirectly probe the mechanism of electron transfer by studying the physical properties (intervalence charge transfer transitions, comproportionation constant, and electronic delocalization and coupling) of the mixed valence (M---M+) states. (B) In the second approach, a series of Ru---Os bipyridyl complexes will be employed to directly measure rates of electron transfer between the metals so as to probe the effect of distance on the rate at a fixed potential. In addition, by changing the substituents on the bipyridyl ligands bound to each metal, the reduction potentials of the two metal sites will be varied in order to study (1) the effect of redox asymmetry on the properties of the mixed valence states and (2) to determine the rate of electron transfer as a function of driving force at constant distance. There have been numerous theoretical treatments of the effects of distance and driving force on the physical properties of mixed valence complexes and on the rate of electron transfer. The data obtained through this overall approach will provide several stringent experimental tests of these theories. It is only through the systematic investigation of structurally defined binuclear metal complexes bridged by non- conjugated ligands that an accurate picture will emerge of the role played by distance and driving force in determining the properties of mixed valence states and the rate of electron transfer between metals.