Chen Chengjian, Chi Zhenguo, Chong Kok Chan, Batsanov Andrei S, Yang Zhan, Mao Zhu, Yang Zhiyong, Liu Bin
Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore, Singapore.
School of Chemistry, Sun Yat-sen University, Guangzhou, China.
Nat Mater. 2021 Feb;20(2):175-180. doi: 10.1038/s41563-020-0797-2. Epub 2020 Sep 21.
Commercial carbazole has been widely used to synthesize organic functional materials that have led to recent breakthroughs in ultralong organic phosphorescence, thermally activated delayed fluorescence, organic luminescent radicals and organic semiconductor lasers. However, the impact of low-concentration isomeric impurities present within commercial batches on the properties of the synthesized molecules requires further analysis. Here, we have synthesized highly pure carbazole and observed that its fluorescence is blueshifted by 54 nm with respect to commercial samples and its room-temperature ultralong phosphorescence almost disappears. We discover that such differences are due to the presence of a carbazole isomeric impurity in commercial carbazole sources, with concentrations <0.5 mol%. Ten representative carbazole derivatives synthesized from the highly pure carbazole failed to show the ultralong phosphorescence reported in the literature. However, the phosphorescence was recovered by adding 0.1 mol% isomers, which act as charge traps. Investigating the role of the isomers may therefore provide alternative insights into the mechanisms behind ultralong organic phosphorescence.
商用咔唑已被广泛用于合成有机功能材料，这些材料在超长有机磷光、热激活延迟荧光、有机发光自由基和有机半导体激光器方面取得了最新突破。然而，商业批次中存在的低浓度异构体杂质对合成分子性质的影响需要进一步分析。在此，我们合成了高纯度咔唑，并观察到其荧光相对于商业样品发生了54nm的蓝移，且其室温超长磷光几乎消失。我们发现这些差异是由于商业咔唑来源中存在浓度<0.5mol%的咔唑异构体杂质。由高纯度咔唑合成的十种代表性咔唑衍生物未能表现出文献报道的超长磷光。然而，通过添加0.1mol%作为电荷陷阱的异构体，磷光得以恢复。因此，研究异构体的作用可能为超长有机磷光背后的机制提供新的见解。
