A New V-Shaped Organic Fluorescent Compound Integrated with Crystallization-Induced Emission Enhancement and Intramolecular Charge Transfer

The emission behavior of a new V-shaped organic fluorescent compound (p,p′-bis(2-aryl-1,3,4-oxadiazol-5-yl)diphenyl sulfone (OZA-SO), consisting of diethylamino (donor) and sulfone (acceptor) units, has been studied in various polar solvents and with different morphologies. As expected, there is the gradual transition from the locally excited state to the intramolecular charge-transfer (ICT) state with the increasing solvent polarity. The photoluminescence intensity of OZA-SO initially decreases with a low water fraction (f_w), owing to ICT effect, and then increases with a high f_w, owing to crystallization-induced emission enhancement. At the same time, the fluorescence lifetime of OZA-SO increases from 0.062 ns in dimethylformamide (DMF) to 5.80 ns in a solution containing 90 % water, and then to 7.49 ns in a solution containing 60 % water. Furthermore, the solid-state emission of OZA-SO can be tuned reversibly from green to yellow by fuming/grinding or fuming/heating owing to morphological changes. This color-switchable feature of OZA-SO may have potential applications in optical-recording and temperature-sensing materials. Flick of a switch: The emission behavior of OZA-SO has been studied in various polar solvents and with different morphologies. The emission behavior can be tuned by solvents, aggregation, and changes in morphology. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.