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Restriction of Photoinduced Twisted Intramolecular Charge Transfer
Author(s) -
Qian Yan,
Cai MinMin,
Xie LingHai,
Yang GuoQiang,
Wu ShiKang,
Huang Wei
Publication year - 2011
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201000457
Subject(s) - enol , intramolecular force , excited state , photochemistry , chemistry , proton , stereochemistry , atomic physics , organic chemistry , catalysis , physics , quantum mechanics
Abstract An intensive investigation of structure–property relationships in the aggregation‐induced enhanced emission (AIEE) of luminescent compounds is essential for the rational design of highly emissive solid‐state materials. In the AIEE‐active compounds N , N ′‐bis[3‐hydroxy‐4‐(2′‐benzothiazolyl)phenyl]isophthalamide and N , N ′‐bis[3‐hydroxy‐4‐(2′‐benzothiazolyl)phenyl]‐5‐ tert ‐butylisophthalamide, fast photoinduced twisted intramolecular charge transfer (TICT) of the enol excited state is found to be mainly responsible for the weak emission of their dilute solutions. The photoinduced TICT enol excited state is formed with a greatly distorted configuration, due to the large rotation about the CN single bond. This facilitates nonradiative TICT decay from the normal enol excited state to the highly twisted enol excited state, rather than proton‐transfer decay to the keto excited state. In aggregates, photoinduced nonradiative deactivation of TICT is strongly prohibited, so that excited‐state intramolecular proton transfer (ESIPT) becomes the dominant decay, and hence contributes greatly to the subsequent emission enhancement of the keto form. Molecular design and investigation of analogous single‐armed compounds further verifies this kind of AIEE mechanism.