Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA, Japan Science and Technology Agency (JST), Suita, Osaka, 565-0871, Japan.
Faraday Discuss. 2012;155:89-102; discussion 103-14. doi: 10.1039/c1fd00084e.
An electron donor-quinolinium ion dyad, 2-phenyl-4-(1-naphthyl)quinolinium ion (QuPh+-NA), has been synthesized based on a rational design. The X-ray crystal structure of QuPh+-NA indicates that the dihedral angle between the NA and QuPh+ moieties of QuPh+-NA is nearly perpendicular. The one-electron reduction potential (E(red)) was observed as a well-defined reversible wave at -0.90 V versus SCE. The one-electron reduced species (QuPh*-NA) was detected by ESR. The electron self-exchange rate constant (k(ex)) between QuPh+-NA and QuPh*-NA has been determined from the ESR linewidth alternation. The reorganization energy (lambda) of the electron self-exchange was determined to be 0.42 eV from the k(ex) value. Femtosecond laser irradiation of QuPh+-NA at 355 nm results in formation of the ET state (QuPh*-NA*+) within 0.5 ps via photoinduced ET from NA to the singlet-excited state of QuPh+. The transient absorption bands at 420 nm and 700 nm are assigned to the QuPh and NA*+ moieties, respectively. The nanosecond laser excitation of QuPh+-NA affords the broad absorption band at 1000 nm and is due to the pi-dimer radical cation formed between QuPh*-NA*+ and QuPh+-NA. The intramolecular back electron-transfer process was too slow to compete with the intermolecular back electron-transfer reaction judging from the decay time profile of QuPh*-NA*+, which obeyed second-order kinetics.
基于合理设计，合成了一个电子给体-醌离子偶联物，2-苯基-4-(1-萘基)喹啉鎓离子(QuPh+-NA)。QuPh+-NA 的 X 射线晶体结构表明，NA 和 QuPh+ 部分之间的二面角几乎垂直。单电子还原电位(E(red))在 -0.90 V 相对于 SCE 处观察到一个明确的可逆波。ESR 检测到单电子还原产物(QuPh*-NA)。通过 ESR 线宽交替，确定了 QuPh+-NA 和 QuPh*-NA 之间的单电子自交换速率常数(k(ex))。从 k(ex)值确定电子自交换的重组能(lambda)为 0.42 eV。355nm 飞秒激光辐照 QuPh+-NA 导致在 0.5 ps 内通过从 NA 到 QuPh+的单重激发态的光诱导 ET 形成 ET 态(QuPh*-NA*+)。420nm 和 700nm 的瞬态吸收带分别归属于 QuPh 和 NA*+部分。QuPh+-NA 的纳秒激光激发在 1000nm 处提供宽吸收带，这是由于在 QuPh*-NA*+和 QuPh+-NA 之间形成的 pi-二聚自由基阳离子。从 QuPh*-NA*+的衰减时间曲线判断，分子内电子反向转移过程太慢，无法与分子间电子反向转移反应竞争，其遵循二级动力学。
