EAPSI:: Investigation of Distance and Orientation Dependence for Electron Transfer Between Organic Molecules

在分子识别和传感、分子电子学、发光二极管、聚合物和液体微环境的测定等方面，有机分子都有广泛的应用。电子转移过程必须满足特定的标准，即胺猝灭剂的孤对电子与芘之间的取向和距离。一般来说，猝灭剂对芳香族分子的接近和距离是从不太确定的数据中推断出来的，其中假设存在有利的相互取向和距离。该奖项支持研究(1)更详细地研究这种类型的电子/电荷转移与距离和取向的关系；以及(2)利用乔治敦大学无法获得的设备分析这一过程。特别是河北科技师范大学张贤福教授中国教授的激光闪光分光光度法。LFS将被用来在电子转移后立即直接检测自由基离子之间的程度和分离距离。我们的研究考察了各种胺的途径以及它们进行电子/电荷转移到四芳基芘(TKPy)分子所需的距离，在TKPy分子中，进入该体系的途径受到限制。在TkPys和芳香胺相互作用的发射中可以观察到电荷转移激发态络合物(激基复合体)的存在。电荷或电子转移的程度取决于络合物形成时猝灭剂与TkPys之间的距离，并且随胺的类型和形状而变化。这些研究得出的结论显然适用于其他各种芳香族化合物的荧光被猝灭的系统。该奖项由东亚和太平洋夏季学院计划资助一名美国研究生的夏季研究，由美国国家科学基金会和中国的科技部联合资助。

The organic molecule, pyrene, is used in a multitude of applications, including molecular recognition and sensing, molecular electronics, light emitting diodes, determination of micro-environments of polymers and liquids, etc. Fluorescence quenching of pyrene with amines proceeds by an electron-transfer mechanism where an amine may donate an electron to the pyrene molecule. The process of electron-transfer must meet specific criteria for the orientation of and distance between the lone pair of electrons of an amine quencher and pyrene. In general, the approach and distance of quenchers to aromatic molecules are inferred from less than definitive data in which the existence of a favorable mutual orientation and distance is assumed. This award supports research (1) to examine in greater detail the distance and orientation dependence of this type of electron/charge transfer; and (2) to analyze this process by equipment not accessible to Georgetown University. Particularly, laser flash spectrophotometry under the expertise of Prof. Xian-Fu Zhang at Hebei Normal University of Science and Technology in Heibei, China. The LFS will be used to examine directly the degree of and separation distance between radical ions immediately after electron-transfer.Our studies examine the approach of a variety of amines and the distance needed for them to undergo electron/charge transfer to tetrakisarylpyrene (TKPy) molecules in which access to the ð-system is restricted. The presence of a charge-transfer, excited-state complex (exciplex) is observable in emission from the interaction between the TkPys and aromatic amines. The degree of charge- or electron-transfer is dependent on the distance between quencher and TkPys at the moment of complex formation, and it varies with the type and shape of the amine. The conclusions obtained from these studies are clearly applicable to a wide variety of other systems in which fluorescence from an aromatic moiety is being quenched.This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Ministry of Science and Technology of China.