From Dark TICT State to Emissive quasi-TICT State: The AIE Mechanism of N-(3-(benzo[d]oxazol-2-yl)phenyl)-4-tert-butylbenzamide

A phenylbenzoxazole-based organic compound, N -(3-(benzo[ d ]oxazol-2-yl)phenyl)-4- tert -butylbenzamide (3OTB), has been synthesized, and the mechanism of its condensed-state emission enhancement has been studied. Experimental and theoretical investigations indicate that prohibition of transition from the local excited state to the nonemissive twisted intramolecular charge transfer (TICT) excited state, but halfway to the intermediate emissive quasi -TICT excited state that results from partial restriction of free intramolecular rotations in condensed states, is responsible for the emission enhancement. Furthermore, it is easy to grow 3OTB nanosheets from THF/H 2 O mixed solvents. In addition, when the molecular arrangement is more ordered, restriction of molecular rotation becomes severer, and consequently, stronger emission can be observed, so that the emission quantum efficiency is in the order of crystalline > powder > nanosheet > amorphous film.