The Dual‐State Luminescent Mechanism of 2,3,4,5‐Tetraphenyl‐1H‐pyrrole

• Published in: Chemistry : a European journal Vol. 24; no. 53; pp. 14269 - 14274
• Main Authors: Lei, Yunxiang, Liu, Qianwei, Dong, Lichao, Cai, Zhengxu, Shi, Jianbing, Zhi, Junge, Tong, Bin, Dong, Yuping
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 20.09.2018
• Subjects: aggregation-induced emission; Chemical synthesis; Chemistry; Conformation; Conjugation; dual-state emission materials; Emission analysis; Emissions control; intermolecular interactions; Position measurement; pyrrole-based molecules; structure–property relationships; Twisting; Viscosity; Dual-state emission materials aggregation -induced emission twisting conformation rigid conjugation
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201803080

2,3,4,5‐Tetraphenyl‐1H‐pyrrole (TePP) was synthesized by a simple one‐step reaction. The compound showed a balanced emission in both the solution and solid state with the absolute quantum yield of ΦF/THF=65.6 % and ΦF/solid=74.3 %, respectively. Temperature and viscosity variation measurements demonstrated that the phenyl group at the 1‐position (N‐position) of the pyrrole core can act as a rotor in pyrrole‐based molecules, which can consume the excited energy and reduce the molecular emission in solution. TePP without the phenyl group at the 1‐position can effectively enhance the emission in solution. Single‐crystal analysis showed that the phenyl groups at the 2,5‐positions of pyrrole extend the molecular conjugation and lock the conformation. The phenyl groups at the 3,4‐positions with a twisted conformation prevent their molecules from close packing and are helpful for aggregated emission. A delicate balance between the twisting conformation and rigid conjugation takes advantage of both ACQ and AIE luminogens. The strategy can tune the AIE, ACQ, or solution and solid dual‐state emission properties of pyrrole‐based molecules by simply altering the position of phenyl groups, which provides a great opportunity to explore the luminescent mechanism in greater detail and to facilitate practical applications. A series of polyarylpyrroles and their optical properties were studied. TePP can emit efficiently in both solution and the aggregated state. Aggregation‐induced emission (AIE), aggregation‐caused quenching (ACQ), and dual‐state emission (DSE) properties can be readily tuned by simply altering the phenyl position at the pyrrole core (see scheme).