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Solvent Effect on the Photoinduced Electron Transfer Reaction Between Thioxanthen-9-one and Diphenylamine
Lin Chen,Qiao-hui Zhou,Xiang Liu,Xiao-guo Zhou*,Shi-lin Liu
Author NameAffiliationE-mail
Lin Chen Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Qiao-hui Zhou Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Xiang Liu Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Xiao-guo Zhou* Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China xzhou@ustc.edu.cn 
Shi-lin Liu Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China  
Abstract:
Photoinduced chemical reaction between thioxanthen-9-one (TX) and diphenylamine (DPA) were investigated by the nanosecond laser flash photolysis. With photolysis at 355 nm, the triplet TX (3TX*) is produced via a Franck-Condon excitation and intersystem crossing. In the transient absorption spectra of the reduction of 3TX* by DPA in pure and aqueous CH3CN, four bands are clearly observed and assigned to absorption of 3TX*, TXH·, TX·- and DPA·+, respectively. With the increase of solvent polarity, the blue-shift was observed for all absorption bands of the intermediates. With the aid of dynamic decay curves, an electron transfer followed by a protonation process is confirmed for the reduction of 3TX* by DPA. The quenching rate constants of 3TX* by DPA very slightly decrease from 9.7×109 L/(mol·s) in pure CH3CN, to 8.7×109 L/(mol·s) in CH3CN:H2O (9:1), 8.0×109 L/(mol·s) in CH3CN:H2O (4:1) and 7.5×109 L/(mol·s) in CH3CN:H2O (1:1). Therefore water plays a minor role in the title reaction, and moreover no obvious medium effect of solvent polarity is observed for the electron transfer between 3TX* and DPA, indicating that the 3* and 3ππ* states of TX have the approximate ability to attract an electron from DPA.
Key words:  Electron transfer, Protonation, Reaction mechanism, Absorption spectra, Laser flash photolysis
FundProject:
光诱导噻吨酮与二苯胺间电子转移反应的溶剂化效应
陈琳,周巧慧,刘香,周晓国*,刘世林
摘要:
利用纳秒激光闪光光解技术研究了噻吨酮(TX)和二苯胺(DPA)的光化学反应.在355 nm光激发下,TX的基电子态跃迁至第一激发态进而通过系间窜越生成三重态3TX*. 在乙腈/水混合溶剂中,3TX*与DPA反应体系的瞬态吸收光谱呈现出四个谱峰,分别对应3TX*、TXH·、TX·-和DPA·+的吸收. 随着溶剂极性的增大,这些吸收峰均发生红移. 结合动力学测量,3TX*与DPA的反应机理被证实为电子转移伴随质子转移过程. 3TX*与DPA反应的猝灭速率常数随溶剂极性的增大而缓慢减小,9.7×109 L/(mol·s)(纯乙腈)、8.7×109 L/(mol·s)(乙腈:水=9:1)、8.0×109 L/(mol·s)(乙腈:水=4:1)和7.5×109 L/(mol·s)(乙腈:水=1:1). 质子溶剂-水在此反应中的作用不明显,溶剂的极性对3TX*与DPA电子转移速率的影响不大,表明3TX*3*3ππ*三重态吸引DPA中电子的能力相仿.
关键词:  电子转移,质子化,反应机理,吸收光谱,激光闪光光解
DOI:10.1063/1674-0068/28/cjcp1503054
分类号: