Highly efficient luminescent E- and Z-isomers with stable configurations under photoirradiation induced by their charge transfer excited states
Highly efficient luminescent E- and Z-isomers with stable configurations under photoirradiation induced by their charge transfer excited states
复制标题
在电荷转移激发态诱导的光照射下具有稳定构型的高效发光 E 和 Z 异构体
DOI：
10.1039/c7tc02474f
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发表时间：
2017-08-28
影响因子：
6.4
通讯作者：
Zhang, Cheng
中科院分区：
文献类型：
--
作者：
Li, Weijun;Wang, Shizhao;Zhang, Cheng
基于双键的高效发光E-/Z-异构体在光照射条件下激发态具有稳定的E/Z构型，对有机光化学和光电子学具有重要意义。本文报道了通过Knovenagel反应同时合成的给体-受体-三苯胺-氰基二苯乙烯分子的高效发光E-/Z-异构体，其E/Z构型由所获得的单晶结构证实。核磁共振谱表明，在光照条件下，E-TPNCF和Z-TPNCF在DMSO-d6溶剂和薄膜中都保持了稳定的E/Z构型。在不同极性溶剂中的原位紫外光谱表明，极性对稳定构型中的E/Z异构体有积极的作用。PL溶致变色实验和理论计算结果表明，在E-TPNCF和Z-TPNCF中，S1态都具有电荷转移(CT)特性。随着溶剂极性的增加，S1态的能量逐渐降低，通过S2态到S1态的快速内转换过程，有效地抑制了高能S2态的E/Z异构化反应。这可能是在光照条件下观察到稳定的E-/Z-异构体的主要原因。光物理研究表明，E-TPNCF和Z-TPNCF在薄膜中都表现出明显的聚集诱导发射(AIE)，其荧光量子效率分别为70%和50%。进一步的研究表明，TPNCF分子中的AIE现象主要是由其CT激发态特征决定的，而不是E/Z异构化或限制的分子内旋转效应。我们的工作将对E/Z异构化反应的基础光化学研究和用于有机光电应用的稳定的E/Z异构体的材料设计有很大的贡献。
Highly efficient luminescent E-/Z-isomers based on double bonds with stable E/Z configurations in the excited state under photoirradiated conditions are of great significance to organic photochemistry and photoelectronics. Herein we report the highly efficient luminescent E-/Z-isomers of a donor–acceptor triphenylamine–cyanostilbene molecule, TPNCF, which were synthesized simultaneously via a Knoevenagel reaction, with their E/Z configurations confirmed by the obtained single crystal structure. The NMR spectra showed that both E-TPNCF and Z-TPNCF maintained their stable E/Z configurations in DMSO-d6 solvent and films under photoirradiation conditions. The in situ UV spectra in different polar solvents showed that polarity played a positive role in stabilizing the E/Z isomers in their configurations. PL solvatochromism experiment and theoretical calculation results indicated that the S1 state has charge-transfer (CT) character in both E-TPNCF and Z-TPNCF. As the solvent polarity increased, the energy of the S1 state gradually decreased, and the E/Z isomerization reaction at the higher energy S2 state was effectively suppressed by a rapid internal conversion process from the S2 to the S1 state. This was supposed to be the main reason for the observed stable E-/Z-isomers under photoirradiated conditions. Photophysical investigations demonstrated that both E-TPNCF and Z-TPNCF exhibited an obvious aggregation-induced emission (AIE) with high fluorescence quantum efficiencies of 70% and 50% in films respectively. Further research revealed that the AIE phenomenon in the TPNCF molecules was mainly dominated by their CT excited state characteristic but not the E/Z isomerization or the restricted intramolecular rotation effect. Our work will contribute considerably to the basic photochemistry studies on E/Z isomerization reactions and the material design of stable E/Z isomers for organic photo-electronic applications.