Theoretical Study On The Excited-state Intramolecular Proton Transfer

In this paper,two kinds of systems that can occur intramolecular proton transfer were investigated.All geometry configurations in both ground and excited states have been optimized without any constraint using the density function theory(DFT)and time-dependent density function theory(TD-DFT)methods,respectively.By analyzing the main structural parameters of the stable configurations and the infrared vibration spectrum of the special functional groups,we have studied the changes of the hydrogen bond after photo-excitation.According to the frontier molecular orbital,absorption and fluorescence spectra,we have investigated the spectral shift and intramolecular charge transfers.In addition,we elaborated on the process and mechanism of intramolecular proton transfer in the excited state.This paper is divided into five chapters.In the first chapter,we introduced a series of the photo-excitation and decay processes of molecular systems,as well as the property and effect of hydrogen bonding in brief.In the second chapter,we introduced several theoretical methods to study the excited state reaction kinetics,including the density function theory and time-dependent density function theory.In the third chapter,we have studied the proton transfer process of 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol in the ground and excited states.Based on the theoretical calculation,we found that the two intramolecular hydrogen bonds are strengthened upon photo-excitation to the excited state,which can promote the proton transfer.According to the analysis of the potential energy surface in the ground and excited states,the results demonstrate that the proton transfer in the excited state is more likely to occur in stepwise.The forth chapter focus on the excited state deactivation mechanism in 2-Amino-3-(2'-Benzazolyl)-Quinolines.We constructed the potential energy curves of the ABO and ABT molecules with the N-H bond lengths fixed at a series of values.By analyzing the potential energy curves,we found that two derivatives of 2-Amino-3-(2'-Benzazolyl)-Quinolines may return to the ground state by radiation after proton transfer in the excited state and may occur the reverse proton transfer reaction immediately before the fluorescence is detected.In the five chapter,we summarized all the work.