CHIN-HUNG LAI2026-10-162026-10-162008-10-24Pure ID: 14994193Pure UUID: 20a8874e-8d3b-48f6-bc73-4329690a422f10.1002/cphc.200800352https://www.scopus.com/pages/publications/54349104683https://scholars.csmu.edu.tw/handle/123456789/28050The interplay between excited-state charge and proton transfer reactions in protic solvents is investigated in a series of 7-azaindole (7AI) derivatives: 3-cyano-7-azaindole (3CNAI), 5-cyano-7-azaindole (5CNAI), 3,5-dicyano-7- azaindole (3,5CNAI) and dicyanoethenyl-7-azaindole (DiCNAI). Similar to 7AI, 3CNAI and 3,5CNAI undergo methanol catalyzed excited-state double proton transfer (ESDPT), resulting in dual (normal and proton transfer) emission. Conversely, ESDPT is prohibited for 5CNAI and DiCNAI in methanol, as supported by a unique normal emission with high quantum efficiency. Instead, the normal emission undergoes prominent solvatochromism. Detailed relaxation dynamics and temperature dependent studies are carried out. The results conclude that significant excited-state charge transfer (ESCT) takes place for both 5CNAI and DiCNAI. The charge-transfer specie possesses a different dipole moment from that of the proton-transfer tautomer species. Upon reaching the equilibrium polarization, there exists a solvent-polarity induced barrier during the proton-transfer tautomerization, and ESDPT is prohibited for 5CNAI and DiCNAI during the excited-state lifespan. The result is remarkably different from 7AI, which is also unique among most excited-state charge/proton transfer coupled systems studied to date.9enjournal article