Time-dependent density functional theory (TDDFT) method was used to study the different excited states proton transfer mechanism of DPP in cyclohexane (CHE) and Methanol (MeOH). The results indicate that the concerted mechanism and the stepwise mechanism coexist in the double proton transfer process of DPP dimer in the aprotic solvent CHE, the stepwise mechanism predominates. The stepwise mechanism can only carry out single proton transfer (DPP-SFr), the second proton cannot be transferred because it is hindered by high energy barriers. The concerted mechanism produces a double proton transfer...
