CHEMICAL MODELS FOR BIOLOGICAL ELECTRON TRANSFER

生物电子转移的化学模型

• 批准号: 3296134
• 负责人: JOHN H DAWSON
• 金额: $ 8.52万
• 依托单位: UNIVERSITY OF SOUTH CAROLINA AT COLUMBIA
• 依托单位国家: 美国
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-02-01 至 1992-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3296134
• 关键词: chemical models; electron transport; ligands; metal complex; metalloenzyme; osmium; oxidation reduction reaction; oxidative phosphorylation; photosynthesis; reduction; ruthenium

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.

许多生物过程批判性地取决于电子 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。 如果是基本 理解这种系统是可以实现的 必须解释效率和选择性。 距离的距离 氧化还原位点与驱动力之间的分离 电子转移反应被认为在 控制电子传输速率。 该提案提出 广泛的研究计划，旨在调查 热电子速率的距离和驱动力 金属之间的转移。 为此，一系列双核金属 在桥接配体的地方将准备复合物 固定的饱和结构定义了两种金属 距离距离，该距离可以系统地距离 变化。 此外，建筑群已经设计为 已知两种金属的还原电位差异，并且 也可以更改。 两种一般方法已经 提出。 （a）在第一个系统中，一系列RU2和OS2 双吡啶基络合物将用于间接探测 通过研究物理的电子转移机制 属性（间隔电荷转移过渡， 组合常数和电子离域和 混合价（M --- M+）状态的耦合。 （b）第二 方法，一系列RU --- OS双吡啶基络合物将是 用于直接测量电子传输速率 金属以探测距离对速率的影响 固定潜力。 另外，通过更改取代基 双吡啶基配体与每种金属结合，还原电位 为了研究（1）效果，这两个金属位点将变化 混合价状态性能上的氧化还原不对称的 （2）确定电子传输速率作为 恒定距离的驱动力。 有很多 距离和驾驶影响的理论治疗 混合价络合物的物理特性和 电子传输速率。 通过此获得的数据 总体方法将提供一些严格的实验测试 这些理论。 只有通过系统的调查 由非 - 共轭配体，将出现准确的图片 距离和驱动力在确定 混合价状态和电子速率的性质 金属之间的转移。