Theoretical Study On The Application Of Fluorescence Probe Molecules Based On Excited State Intramolecular Proton Transfer Mechanism In Biological Detection

Excited intramolecular proton transfer is one of the most important reactions in the biological field.At the same time,excited intramolecular proton transfer(ESIPT)plays an important role in fluorescent probes and has received extensive attention and research,which has been widely used in biological detection.Therefore,what does the role of proton transfer in excited molecules play in the detection of biological probes? What's the impacts of the environment and molecular twisting on the ESIPT? Moreover,how does the mechanism of ESIPT affect the design of probes? The above is the focus of this thesis.In this thesis,we will use density functional theory and time-dependent density functional theory methods combined with polarization continuous solvation model to carry out in-depth study on the ESIPT mechanism of fluorescent probe system.We have performed theoretical studies on the three probe molecules:(1)Through the theoretical calculations of the ESIPT reactions of N-(2-(4-(Dimethylamino)phenyl)-3-hydroxy-4-oxo-4H-chromen-6-yl)butyramide(NDHB)molecule in the three kinds of solvents,it was found that as the dielectric constant of the solvent reducing,the ESIPT reaction was conducive to occur.Meanwhile,the wavelength of the fluorescence could be affected by the solvation.(2)By studying the ESIPT process of 3-hydroxyflavone derivative 2-(4-(Diethylamino)phenyl)-3-hydroxy-4H-chromen-4-one(DHC)in the four kinds of solvents,we found that after excited by lighting,DHC molecules would twist,which is one of the reasons for the dual fluorescent of DHC.In addition,the effect of the solvation on the ESIPT was also studied,and it was found that as the dissolution dielectric constant decreasing,the ESIPT was easy to occur.However,when the dielectric constant was decreased,it was not conducive to the near infrared fluorescence emitted by DHC molecules.(3)Two possible ESIPT pathways of 3-hydroxytryptone derivatives in acetonitrile solvent were studied.By optimizing the three conformations and constructing the potential energy surfaces,it was proved that DH3B2-C was the main conformation of DH3B2 molecule for the first time.Therefore,the main pathway of ESIPT was determined and the mechanism in detail was clarified.It was of great significance for the design of fluorescent probes for biological monitoring of DH3B2 molecules.In a word,all the quantitative calculation method selected in our research is reasonable and reliable.In the theoretical point of view,the mechanism of the probe molecule used for biological monitoring has been explained.The explanation of the mechanism is insufficient in the experiment,thus,our calculation results could provide supplements and corrections for the experiment.