Karimata Ayumu, Suzuki Shuichi, Kozaki Masatoshi, Kimoto Kenshi, Nozaki Koichi, Matsushita Hironori, Ikeda Noriaki, Akiyama Kimio, Kosumi Daisuke, Hashimoto Hideki, Okada Keiji
Department of Chemistry, Graduate School of Science and ⊥Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka City University , Sumiyoshi-ku, Osaka, 558-8585, Japan.
J Phys Chem A. 2014 Nov 26;118(47):11262-71. doi: 10.1021/jp509643q. Epub 2014 Nov 12.
Photoinduced intramolecular electron transfer of dyad PTZ3-PTZ2-PTZ1-B-AQ consisting of phenothiazine trimer (PTZ3-PTZ2-PTZ1), bicyclo[2.2.2]octane (B), and anthraquinone (AQ) was investigated. After excitation (∼20 ps) of the AQ moiety in THF, a metastable radical ion pair (RIP) PTZ3-PTZ2-PTZ1(+)-B-AQ(-) appeared at ∼620 nm. From 500 ps to 6 ns the spectrum changed to a new absorption (∼950 nm), which was assigned to the hole-shifted stable RIP state PTZ3-PTZ2(+)-PTZ1-B-AQ(-). The time constant of the hole-shift process was determined to be 6.0 ns. The hole-shifted RIP state had a lifetime (τ) of 250 ns and was characterized by spin-polarized signals as a spin-correlated radical pair (SCRP) by means of time-resolved ESR. These results were compared with those for the phenothiazine monomer analog PTZ-B-AQ, which also produced the RIP state PTZ(+)-B-AQ(-) with τ = 1.9 μs. Time-resolved ESR showed an all emission signal pattern showing the triplet mechanism of PTZ-B-(3)AQ* → (3)[PTZ(+)-B-AQ(-)]. The origin of the difference in the lifetimes between the trimer and the monomer RIP states was discussed from various points of view, including free energy difference in the RIP states, reorganization energy difference in the charge recombination process, and the spin-state difference. Of these, the spin-state difference effect provided the most reasonable explanation.
研究了由吩噻嗪三聚体（PTZ3-PTZ2-PTZ1）、双环[2.2.2]辛烷（B）和蒽醌（AQ）组成的二元体系PTZ3-PTZ2-PTZ1-B-AQ的光诱导分子内电子转移。在四氢呋喃中对AQ部分进行激发（约20皮秒）后，在约620纳米处出现了亚稳态自由基离子对（RIP）PTZ3-PTZ2-PTZ1(+)-B-AQ(-)。从500皮秒到6纳秒，光谱变为新的吸收峰（约950纳米），这被归因于空穴转移的稳定RIP态PTZ3-PTZ2(+)-PTZ1-B-AQ(-)。空穴转移过程的时间常数被确定为6.0纳秒。空穴转移的RIP态的寿命（τ）为250纳秒，并通过时间分辨电子自旋共振表征为自旋极化信号，即自旋相关自由基对（SCRP）。将这些结果与吩噻嗪单体类似物PTZ-B-AQ的结果进行了比较，PTZ-B-AQ也产生了τ = 1.9微秒的RIP态PTZ(+)-B-AQ(-)。时间分辨电子自旋共振显示了全发射信号模式，表明了PTZ-B-(3)AQ* → (3)[PTZ(+)-B-AQ(-)]的三重态机制。从包括RIP态的自由能差、电荷复合过程中的重组能差以及自旋态差等多个角度讨论了三聚体和单体RIP态寿命差异的起源。其中，自旋态差效应提供了最合理的解释。
