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Direct Observation of Ultrafast Relaxation Dynamics of a Mixed Excimer State in Perylene Monoimide Dimer by Femtosecond Transient Absorption
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2023-03-03 , DOI: 10.1021/acs.jpclett.3c00106 Chaochao Qin 1 , Zheng Zhang 1 , Qiaoling Xu 2 , Jian Song 1 , Zhaoyong Jiao 1 , Shuhong Ma 1 , Ruiping Qin 3 , Yuhai Jiang 4
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2023-03-03 , DOI: 10.1021/acs.jpclett.3c00106 Chaochao Qin 1 , Zheng Zhang 1 , Qiaoling Xu 2 , Jian Song 1 , Zhaoyong Jiao 1 , Shuhong Ma 1 , Ruiping Qin 3 , Yuhai Jiang 4
Affiliation
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A J-type dimer PMI-2, two perylene monoimides linked by butadiynylene bridger was prepared, and its excited-state dynamics was studied using ultrafast femtosecond transient absorption spectroscopy, along with steady-state spectroscopy and quantum chemical calculations. It is evidently demonstrated that the symmetry-breaking charge separation (SB-CS) process in PMI-2 is positively mediated by an excimer, which is mixed by localized Frenkel excitation (LE) and an interunit charge transfer (CT) state. Kinetic studies show that, with the polarity increasing of the solvent, the transformation of excimer from a mixture to the CT state (SB-CS) is accelerated, and the recombination time of the CT state is reduced obviously. Theoretical calculations indicate that these are due to PMI-2 obtaining more negative free energy (ΔGcs) and lower CT state energy levels in highly polar solvents. Our work suggests that the mixed excimer can be formed in a J-type dimer with suitable structure, in which the charge separation the process is sensitive to the solvent environment.
中文翻译：
通过飞秒瞬态吸收直接观察苝单酰亚胺二聚体中混合准分子态的超快弛豫动力学
制备了 J 型二聚体 PMI-2，两个苝单酰亚胺通过丁二炔基桥接物连接，并使用超快飞秒瞬态吸收光谱、稳态光谱和量子化学计算研究了其激发态动力学。显然证明了 PMI-2 中的对称性破缺电荷分离 (SB-CS) 过程是由准分子正介导的，准分子由局部 Frenkel 激发 (LE) 和单元间电荷转移 (CT) 状态混合。动力学研究表明，随着溶剂极性的增加，准分子从混合物向CT态（SB-CS）的转变加快，CT态的复合时间明显缩短。理论计算表明，这是由于PMI-2获得了更多的负自由能（ΔGcs ) 和在高极性溶剂中较低的 CT 态能级。我们的工作表明，混合准分子可以形成具有合适结构的 J 型二聚体，其中电荷分离过程对溶剂环境敏感。
更新日期：2023-03-03
中文翻译：
通过飞秒瞬态吸收直接观察苝单酰亚胺二聚体中混合准分子态的超快弛豫动力学
制备了 J 型二聚体 PMI-2，两个苝单酰亚胺通过丁二炔基桥接物连接，并使用超快飞秒瞬态吸收光谱、稳态光谱和量子化学计算研究了其激发态动力学。显然证明了 PMI-2 中的对称性破缺电荷分离 (SB-CS) 过程是由准分子正介导的，准分子由局部 Frenkel 激发 (LE) 和单元间电荷转移 (CT) 状态混合。动力学研究表明，随着溶剂极性的增加，准分子从混合物向CT态（SB-CS）的转变加快，CT态的复合时间明显缩短。理论计算表明，这是由于PMI-2获得了更多的负自由能（ΔGcs ) 和在高极性溶剂中较低的 CT 态能级。我们的工作表明，混合准分子可以形成具有合适结构的 J 型二聚体，其中电荷分离过程对溶剂环境敏感。
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