Exploitation of Primitive Molecular Recognition Effects in Electron Transfer Reactions

西北大学的Hupp教授将在无机、生物无机和有机金属项目的支持下，研究分子识别对电子转移速率的影响。他计划探索电子转移反应的两个基本方面，一个是溶剂化势垒的分子方面，另一个是中间介质对给体/受体电子耦合强度的影响。他将进行四个班的实验来评估这些问题。1)溶液中的冠醚将与D/A络合物结合，这种结合将模拟溶剂化的分子方面。2)给体和受体将被捕获在半碳中，对双分子电子转移的影响也将模拟溶剂化的分子方面。3)桥联配体为冠醚或相关部分的D/A络合物将通过与阳离子的结合来考察；这将提供关于偶合强度的影响的信息。4)D/A络合物将作为桥联配体构象的函数进行研究；这将提供有关门控电子转移的信息，这将有助于解释第三部分中的研究。这些研究的总体结果将增强对长距离电子转移如何受干预和周围介质影响的理解。化学反应的主要类型之一是电子从一个原子转移到另一个原子。这甚至可以发生在很长的距离上，当两个原子分开时，因为它们驻留在巨大的分子中，或者因为它们驻留在同一分子中的遥远位置。在这种情况下，电子转移速率对中间介质和周围的溶剂都非常敏感。为了对这些效应有一个大致的了解，实验将通过检查专门为此目的而设计的分子中的电子转移来进行。特别是，将研究“分子识别”的各个方面。分子识别意味着一个分子的特定结构特征将导致它以一种高度受控的方式与另一个分子结合；这种结合将导致直接归因于结合分子的已知方面的速度的影响。

Professor Hupp of Northwestern University will investigate the effects of molecular recognition on electron transfer rates with support from the Inorganic, Bioinorganic, and Organometallic Program. He plans to probe two fundamental aspects of electron transfer reactions, one being the molecular aspects of the solvation barrier, the other being the influence of the intervening medium on the donor/acceptor electronic coupling strength. He will conduct four classes of experiments to assess these issues. 1) Crown ethers in solution will bind to D/A complexes, and this binding will simulate the molecular aspects of solvation. 2) Donors and acceptors will be trapped inside hemicarcerands, and the influence on bimolecular electron transfer will likewise simulate the molecular aspects of solvation. 3) D/A complexes where the bridging ligand is a crown ether or related moiety will be examined vis-a-vis their binding of cations; this will give information on the effects on coupling strength. 4) D/A complexes will be examined as a function of the conformation of the bridging ligand;this will give information about gated electron transfer and it will help in the interpretation of the studies in part 3. The general outcome of these studies will be an enhanced understanding of how electron transfer over long distances is affected by the intervening and surrounding media. %%% One of the major types of chemical reaction is electron transfer from one atom to another. This can even occur over long distances, when the two atoms are separated because they reside in bulky molecules, or because they reside in remote sites within the same molecule. Under such circumstances the rates of electron transfer are quite sensitive to the intervening medium and also to the surrounding solvent. Experiments to gain a general understanding of these effects will be undertaken by examining electron transfer in molecules that have been designed specifically for this purpose. In particular, aspects of "molecular recognition" will be investigated. Molecular recognition means that the specific structural features of one molecule will cause it to bind to another molecule in a highly controlled way; this binding will then lead to effects on the rates that can be directly attributed to known aspects of the bound molecule.