Yoshino Keisuke, Sakai Hayato, Shoji Yoshiaki, Kajitani Takashi, Anetai Hayato, Akutagawa Tomoyuki, Fukushima Takanori, Tkachenko Nikolai V, Hasobe Taku
Department of Chemistry, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan.
Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan.
J Phys Chem B. 2020 Dec 31;124(52):11910-11918. doi: 10.1021/acs.jpcb.0c09754. Epub 2020 Dec 18.
We report the first synthesis of solvent-free pentacene fluids at room temperature together with observation of singlet fission (SF). Three pentacenes with different number of ethylene glycol (EG) side chains () were employed (denoted as (EG)-Pc-(EG): = 2, 3, and 4). The morphologies of these pentacenes largely depend on the lengths of EG chains (). (EG)-Pc-(EG) and (EG)-Pc-(EG) indicate fluid compounds at room temperature, whereas (EG)-Pc-(EG) is a solid compound. Microscopic clustering with short-range interactions between pentacene chromophores was confirmed in X-ray diffraction profiles of solvent-free fluids. Such a structural trend is an important origin of SF and consistent with the steady-state spectroscopic results. To one's surprise, femtosecond transient absorption spectroscopy demonstrated that SF occurred in thin films prepared from solvent-free fluids of (EG)-Pc-(EG) and (EG)-Pc-(EG) in spite of such excessive EG chains.
我们报道了室温下无溶剂并五苯流体的首次合成以及单重态裂变（SF）的观测。使用了三种具有不同数量乙二醇（EG）侧链（）的并五苯（表示为(EG)-Pc-(EG)： = 2、3和4）。这些并五苯的形态在很大程度上取决于EG链的长度（）。(EG)-Pc-(EG)和(EG)-Pc-(EG)在室温下为流体化合物，而(EG)-Pc-(EG)是固体化合物。在无溶剂流体的X射线衍射图谱中证实了并五苯发色团之间存在短程相互作用的微观聚集。这种结构趋势是SF的一个重要起源，并且与稳态光谱结果一致。令人惊讶的是，飞秒瞬态吸收光谱表明，尽管存在过量的EG链，但在由(EG)-Pc-(EG)和(EG)-Pc-(EG)的无溶剂流体制备的薄膜中仍发生了SF。
