An efficient D–A dyad for solvent polarity sensor

An efficient donor (D)–acceptor (A) molecule (6) was synthesized by bonding tercarbazole to phthalimide through a flexible bridge. Structures of 6 and related intermediates were fully characterized by 1H NMR, 13C NMR, and MS as well. Moreover, absorption and emission spectra of 6 and tercarbazole (4) were studied comparatively. As a result, dual emission of 6 was observed in non-polar solvents, while the lifetime consisted of biexponential decays. A longer lifetime emission (18.9 ns) was found due to the exciplex formation through intramolecular charge transfer (ICT) in cyclohexane. The relative intensity of long-wavelength emission was sensitive to solvent polarity. Therefore, 6 has the potential usage as solvent polarity sensor.