CHEMICAL MODELS FOR BIOLOGICAL ELECTRON TRANSFER

生物电子转移的化学模型

• 批准号: 3296133
• 负责人: JOHN H DAWSON
• 金额: $ 8.35万
• 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/3296133
• 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。 如果有基本的 要实现对此类系统的理解，它们的非凡之处 必须解释效率和选择性。 的距离为 氧化还原位点之间的分离和驱动力 电子转移反应被认为起着至关重要的作用 控制电子转移速率。 该提案提出 旨在探讨影响的广泛研究计划 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 将在桥连配体所在的位置制备复合物 饱和结构将两种金属牢固地固定在规定的位置 相隔的距离以及可以系统地计算该距离的位置 多种多样。 此外，综合体的设计使得 两种金属的还原电位差是已知的并且 也可以改变。 有两种通用方法 提出。 (A) 在第一个系统中，一系列 Ru2 和 Os2 联吡啶配合物将用于间接探测 通过研究电子转移的物理机制 性质（间隔电荷转移跃迁， 压缩常数、电子离域和 混合价态（M---M+）的耦合）。 (B) 在第二个 方法，一系列Ru---Os联吡啶配合物将被 用于直接测量之间的电子转移速率 金属以探测距离对速率的影响 固定电位。 此外，通过改变上的取代基 联吡啶配体与每种金属结合，还原电位 为了研究 (1) 的影响，将改变两个金属位点 氧化还原不对称性对混合价态性质的影响 (2) 确定电子转移速率与 恒定距离下的驱动力。 已经有无数 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 关于电子转移速率。 通过这个得到的数据 整体方法将提供多项严格的实验测试 这些理论。 只有通过系统的调查 结构确定的双核金属配合物由非桥接 共轭配体，将出现准确的图像 距离和驱动力在决定 混合价态的性质和电子速率 金属之间的转移。