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

有机分子，芘，被用于许多应用中，包括分子识别和传感，分子电子学，发光二极管，聚合物和液体的微环境的测定等。芘与胺的荧光猝灭通过电子转移机制进行，其中胺可以向芘分子提供电子。 电子转移过程必须满足胺猝灭剂和芘的孤对电子的取向和距离的特定标准。 一般来说，猝灭剂与芳香族分子的接近和距离是从不确定的数据推断的，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/电荷转移的距离和方向依赖性;（2）通过乔治敦大学无法获得的设备分析这一过程。特别是在中国河北科技师范大学的张先福教授的专业知识下，激光闪光分光光度法。 LFS将被用来直接检查的程度和自由基离子之间的分离距离在电子转移后立即。我们的研究检查了各种胺的方法和所需的距离，为他们进行电子/电荷转移到四芳基芘（TKPy）分子中，进入的电子-系统是有限的。 电荷转移，激发态复合物（激基复合物）的存在下，可观察到从TkPys和芳香胺之间的相互作用的发射。 电荷转移或电子转移的程度取决于络合物形成时猝灭剂和TkPys之间的距离，并且它随胺的类型和形状而变化。 从这些研究中获得的结论显然适用于各种各样的其他系统，其中芳香族基团的荧光被猝灭。该奖项是东亚和太平洋夏季研究所计划下的一个美国研究生的夏季研究，由NSF和中国科学技术部共同资助。

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.