Qin Chaochao, Zhang Zheng, Xu Qiaoling, Song Jian, Jiao Zhaoyong, Ma Shuhong, Qin Ruiping, Jiang Yuhai
Henan Key Laboratory of Infrared Materials & Spectrum Measures and Applications, and School of Physics, Henan Normal University, Xinxiang, 453007, China.
School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, 453007, China.
J Phys Chem Lett. 2023 Mar 16;14(10):2455-2462. doi: 10.1021/acs.jpclett.3c00106. Epub 2023 Mar 3.
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 (Δ) 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.
制备了一种J型二聚体PMI-2，它是由丁二炔撑桥连接的两个苝单酰亚胺，并利用超快飞秒瞬态吸收光谱以及稳态光谱和量子化学计算研究了其激发态动力学。结果表明，PMI-2中的对称破缺电荷分离（SB-CS）过程由准分子正向介导，该准分子由局域化的弗伦克尔激发（LE）和单元间电荷转移（CT）态混合而成。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）的转变加速，CT态的复合时间明显缩短。理论计算表明，这是由于PMI-2在高极性溶剂中获得了更多的负自由能（Δ）和更低的CT态能级。我们的工作表明，在具有合适结构的J型二聚体中可以形成混合准分子，其中电荷分离过程对溶剂环境敏感。
