Unraveling photoexcitation dynamical behavior for bis (salicylidene)‐1,5‐diaminonaphthalene (BSD) system

Abstract

AbstractIn this work, a new excited state intramolecular proton transfer (ESIPT) mechanism of bis (salicylidene)‐1,5‐diaminonaphthalene (BSD) is proposed based on density functional theory (DFT) and time‐dependent DFT methods. Given the intramolecular dual hydrogen bonds of BSD, we explore the excited state hydrogen bonding interactions for BSD and verify that the dual intramolecular hydrogen bonds of BSD molecule should be strengthened in the first excited state. Further, in the analyses about charge distribution upon excitation, we confirm that the charge redistribution around hydrogen bonding moieties plays important roles in enhancing dual hydrogen bonds and in facilitating ESIPT process. To reveal the detailed ESIPT mechanism, we construct the potential energy surfaces (PESs) in both S0 and S1 states along with hydrogen bonds. Via comparing potential energy barriers among the stable structures on the S1‐state PES, we present the excited state intramolecular single proton transfer mechanism for BSD system. Moreover, the phenomenon and properties of fluorescence for BSD in experiment could be explained reasonably based on the ESIPT mechanism presented in this work.