Zhang Zhao-Ming, Miao Bao-Xi, Tang Xin-Xue, Ni Zhong-Hai
School of Chemical Engineering and Technology, China University of Mining and Technology Xuzhou 221116 People's Republic of China
Graduate School of Chemical Sciences and Engineering, Hokkaido University Sapporo 001-0021 Japan.
RSC Adv. 2018 Apr 24;8(27):15173-15180. doi: 10.1039/c8ra00057c. eCollection 2018 Apr 18.
By controlling the number of 4,5,9,10-tetrahydropyrene segments around the tetraarylethene core, a series of 4,5,9,10-tetrahydropyrene-based tetraarylethenes were synthesized and structurally characterized. An aggregation-induced emission (AIE) study indicated that all the compounds are AIE active: they are weak emitters in good solvents but highly emissive in the condensed phase, and hence are potential solid-state emitters. Their optical properties, electrochemical properties and theoretical calculations were investigated, and the results prove that the π-conjugation degree of these compounds increases with the increasing number of 4,5,9,10-tetrahydropyrene units. However, the fluorescence quantum yield in the solid state doesn't increase with increasing π-conjugation. We studied the reason for this by analyzing the crystal structures of some compounds, and proposed that the close degree of molecular packing in the solid state may be responsible for it. Loose packing of tetraarylethenes in the solid state can restrict the rotation of the aromatic rings but cannot constrain other non-radiative pathways efficiently, such as vibration, which leads to the unpredictable emission of the compounds.
通过控制四芳基乙烯核周围4,5,9,10-四氢芘片段的数量，合成了一系列基于4,5,9,10-四氢芘的四芳基乙烯，并对其结构进行了表征。聚集诱导发光（AIE）研究表明，所有化合物均具有AIE活性：它们在良溶剂中为弱发光体，但在凝聚相中具有高发射性，因此是潜在的固态发光体。研究了它们的光学性质、电化学性质和理论计算，结果证明这些化合物的π共轭程度随着4,5,9,10-四氢芘单元数量的增加而增加。然而，固态下的荧光量子产率并未随着π共轭的增加而增加。我们通过分析一些化合物的晶体结构研究了其原因，并提出固态下分子堆积的紧密程度可能对此负责。四芳基乙烯在固态下的松散堆积可以限制芳环的旋转，但不能有效地抑制其他非辐射途径，如振动，这导致了化合物不可预测的发射。
