Mechano-induced persistent room-temperature phosphorescence from purely organic moleculesElectronic supplementary information (ESI) available: Synthetic procedures, experimental details and supplemental figures. CCDC 1581141. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8sc00429c

• Main Authors: Mu, Yingxiao, Yang, Zhiyong, Chen, Junru, Yang, Zhan, Li, Wenlang, Tan, Xianbao, Mao, Zhu, Yu, Tao, Zhao, Juan, Zheng, Shizhao, Liu, Siwei, Zhang, Yi, Chi, Zhenguo, Xu, Jiarui, Aldred, Matthew. P
• Format: Article
• Language: English
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c8sc00429c

The persistent room-temperature phosphorescence (RTP) of purely organic materials in the solid state has recently attracted much research interest and found promising, rapid and visual applications by the naked eye, after the removal of the excitation source. However, almost all reported organic persistent RTP processes are induced by using a UV-light irradiation source. In this report, persistent RTP with an emission lifetime as long as 0.15 s which can be induced not only by photoirradiation but also by mechanical action is presented, which merges mechano-induced luminescence and persistent RTP together. It is found that such persistent RTP is produced through intermolecular electronic coupling (IEC) of units with different excited state configurations. Interestingly, there are two different crystals with and without mechano-induced persistent RTP which can be grown from this organic material, as such a new type of mechano-luminescence (ML) is strongly dependent on their intermolecular interactions. Furthermore, the intensity of such mechano-induced persistent RTP can be increased by lowing the temperature as well, similar to that of photo-induced persistent RTP. Notably, these two crystals exhibit a ML enhancement and ML "turn on", respectively, with decreasing temperature. Therefore, such mechano-induced persistent RTP provides an example of new types of organic luminescent materials, which is a missing jigsaw piece of organic luminescence and important for both fundamental research and practical applications of both persistent RTP and ML of organic materials. Interesting purely organic persistent room-temperature phosphorescence induced by not only photoirradiation but also mechanical action has been presented.