Liu Yan, Li Aisen, Ma Zhimin, Xu Weiqing, Ma Zhiyong, Jia Xinru
Beijing State Key Laboratory of Organic-Inorganic Composites, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
State Key Laboratory for Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Physics, Jilin University, Changchun 130012, China.
Phys Chem Chem Phys. 2020 Sep 8;22(34):19195-19201. doi: 10.1039/d0cp02783a.
In this article, we design and synthesize a new carbazole-based molecule, Cz2CN, with a twisted D-A structure, using the carbazole group as the donor and a dicyanoethylene fragment as the acceptor. Such a twisted D-A structure endows Cz2CN with two characteristic emission bands, LE emission and ICT emission. Cz2CN exhibits AIEE, solvatochromism, and different responses to anisotropic shearing force and isotropic hydrostatic pressure, due to the sensitivity of ICT emission to aggregation, solvent polarity and mechanical force. Aggregation benefits the ICT emission, leading to the AIEE of Cz2CN in the THF/water system. Polar solvents can help stabilize the ICT-excited states and make the ICT emission red shift. The original crystalline powder is strongly fluorescent with a high quantum yield of 40.4%. A single crystal of Cz2CN is obtained and dimers without π-π interactions among carbazole groups contribute to the strong emission. Anisotropic shearing alters the emission of Cz2CN powder from sky blue (474 nm) to green (520 nm). The single crystal of Cz2CN undergoes a distinct multicolored variation from sky blue (476 nm) to green (510 nm) and further to orange (590 nm) upon isotropic hydrostatic pressure. The emission of the original powder/crystal of Cz2CN is dominated by LE (locally excited state) emission in HLCT (intercrossed hybridized local and charge transfer excited state). To the best of our knowledge, Cz2CN is an interesting carbazole-based molecule that shows simultaneous AIEE, solvatochromism and force-induced multicolored variation.
在本文中，我们设计并合成了一种新型的基于咔唑的分子Cz2CN，其具有扭曲的D-A结构，以咔唑基团作为供体，二氰基乙烯片段作为受体。这种扭曲的D-A结构赋予Cz2CN两个特征发射带，即LE发射和ICT发射。由于ICT发射对聚集、溶剂极性和机械力敏感，Cz2CN表现出聚集诱导发光增强（AIEE）、溶剂致变色以及对各向异性剪切力和各向同性静水压力的不同响应。聚集有利于ICT发射，导致Cz2CN在四氢呋喃/水体系中出现AIEE现象。极性溶剂有助于稳定ICT激发态并使ICT发射发生红移。原始结晶粉末具有强烈荧光，量子产率高达40.4%。获得了Cz2CN的单晶，咔唑基团之间没有π-π相互作用的二聚体有助于产生强发射。各向异性剪切使Cz2CN粉末的发射从天蓝色（474 nm）变为绿色（520 nm）。在各向同性静水压力下，Cz2CN单晶经历从天蓝色（476 nm）到绿色（510 nm）再到橙色（590 nm）的明显多色变化。Cz2CN原始粉末/晶体的发射在HLCT（交叉杂化局域和电荷转移激发态）中以LE（局域激发态）发射为主。据我们所知，Cz2CN是一种有趣的基于咔唑的分子，它同时表现出AIEE、溶剂致变色和力致多色变化。
