Effects of electron-accepting substituents on the fluorescence of oxygen-bridged triarylamine

New electron-accepting oxygen-bridged triphenylamines were synthesized with nitro and dimesitylboryl sub-stituents. Using optical and electrochemical characterization, the effect of electron-withdrawing substituents on quasi-planar triarylamine skeletons was clarified. Compared with the unbridged nitro-substituted triphenylamine reference, the oxygen-bridged structure featured a smaller optical gap, shifting the absorption and fluorescence wavelengths to longer wavelengths. Structural relaxation in the electronically excited state was suppressed, and the Stokes shift was reduced. Replacing the nitro substituent with a dimesitylboryl group resulted in an increase in the fluorescence quantum yield due to the suppression of the vibronic coupling.