R-D-A and R-D-?-A Structured AIEgens: Relationship between Electronic, Conformational Characteristics and Photophysical Properties

The design of new aggregation-induced emissionluminogens (AIEgens) has aroused continuous attention. Therelationship between structure and performance plays an importantrole in guiding such efforts. In this contribution, two R-D-A- andR-D-pi-A-type AIEgens were facilely designed and synthesized,that is,DPE-PTZ-CNandDPE-PTZ-PCN, with diphenylethyleneas the twisted rotor structure (R), phenothiazine as electron-donor(D), and the (aryl) cyano group as electron-acceptor (A)fragments. Both luminophores were endowed with typical AIEproperties, while their alpha AIE(PL intensity ratio of AIEgen in a mixedsolution with water fraction (fw) = 90 vol % to that withfw=0)were quite different. The alpha AIEforDPE-PTZ-CNwas as high as 41,but it was only 3 forDPE-PTZ-PCN, in which the pi-bridge (aryllinker) was introduced between its D and A groups. In addition, the push-pull electronic effect endowed both molecules with thefeature of intramolecular charge transfer (ICT). The solvatochromism effect observed in solutions with different polarities confirmedthe existence of the ICT process. The theoretical calculation and single crystal structure analysis revealed that the electronic structureand molecular conformation characteristics had a decisive influence on the differences in photophysical behaviors