Electronically excited state structures and stabilities of organic small molecules: A DFT study of triphenylamine derivatives

Abstract Information on the structures and stabilities of electronically excited organic small molecules is critically important for their many applications. In this work, we report the results of excited state structures and stabilities of eight triphenylamine-based molecules from density functional theory calculations. Four functionals, B3LYP, M06-2X, CAM-B3LYP, and ωB97X-D were tested and comparisons with the experimental fluorescence spectra show that B3LYP is a feasible choice. The results illustrated that functionalization of 4-vinyl-N,N-di(p-tolyl)aniline (MTPA) with electron donating groups enhances the C C bond conjugation in the excited state while that with strong electron withdrawing groups does not. With the increase in the electron-withdrawing ability of the substituent, the structural stability of the excited state is relatively independent of the functional groups if the molecule does not form charge separated states. These results will be very helpful for their applications in molecular engineering and rational design of organic photovoltaic materials.