Wang Xuemin, Wang Rui, Shen Li, Tang Zhaofeng, Wen Congying, Dong Bin, Liu Heyuan, Zhang Chunfeng, Li Xiyou
College of Science, China University of Petroleum (East China), Qingdao, Shandong 266580, China.
Phys Chem Chem Phys. 2018 Feb 28;20(9):6330-6336. doi: 10.1039/c7cp07841b.
A covalently linked tetracene trimer with a "face-to-face" stacked structure was prepared and its molecular structure is characterized by H NMR, MALDI-TOF mass spectroscopy, and elemental analysis. The minimized molecular structure reveals that three tetracene subunits within this trimer adopt a partially "face-to-face" stacked configuration. Its absorption spectrum differs significantly from that of the monomeric and dimeric counterparts in solution due to the strong ground state interactions between the neighboring tetracene subunits. Its fluorescence is almost quenched completely. An ultrafast fluorescence decay component is observed in its fluorescence dynamics, indicating the presence of an ultrafast nonradiative decay channel in the trimer. The nonradiative channel is proved to be intramolecular singlet fission (iSF) by femto-second transient absorption studies. Different from the strongly coupled triplet state observed in the corresponding dimer, weakly coupled triplet states can be formed in this trimer. The triplet quantum yield of trimer 4 can reach up to 126% in solution.
制备了具有“面对面”堆积结构的共价连接的并四苯三聚体，并通过核磁共振氢谱（¹H NMR）、基质辅助激光解吸电离飞行时间质谱（MALDI-TOF）和元素分析对其分子结构进行了表征。最小化的分子结构表明，该三聚体内的三个并四苯亚基采用了部分“面对面”的堆积构型。由于相邻并四苯亚基之间强烈的基态相互作用，其吸收光谱与溶液中单体和二聚体对应物的吸收光谱有显著差异。其荧光几乎完全猝灭。在其荧光动力学中观察到一个超快荧光衰减成分，表明该三聚体中存在一个超快非辐射衰减通道。通过飞秒瞬态吸收研究证明，该非辐射通道为分子内单重态裂变（iSF）。与相应二聚体中观察到的强耦合三重态不同，该三聚体中可以形成弱耦合三重态。三聚体4在溶液中的三重态量子产率可达126%。
