Excited-state intramolecular proton transfer (ESIPT) of 1,8-di(pyridin-2-yl)-9H-carbazole (DPyCz) was investigated using static and excited-state dynamic simulations. Three-distinct configurations, each involving a different pyridyl moiety forming an intramolecular hydrogen bond, were identified to explore the competition in ESIPT. Additionally, slower PT, occurring at ∼200 fs, was found to depend on the competition between the pyridyl nitrogen atoms as acceptors. In contrast, DPyCz-B, which features only a single acceptor site, facilitated twice faster PT than that of DPyCz-A. Thus, our findings suggested that the ESIPT process of DPyCz is possibly governed by the interplay of intramolecular hydrogen bonding and excited-state charge redistribution.
