Study On The Intramolecular Proton Transfer Of Aniline Derivatives

Photoinduced excited state proton transfer is an essential process of life and nature.By studying the photophysical and photochemical behaviors of model compounds,it is helpful to understand these basic processes.Related research has become one of the frontier topics in photochemical field.For example,photosynthesis,vision,transmission of nerve impulses or breathing and other life activities are involved in proton movement.Although the proton transfer to do a detailed molecular mechanism,but there are still many can be explored for a long time.In this paper,the intramolecular proton transfer processes of aniline derivatives were studied by combination of theory and experiment.The excited state proton transfer of N-phenylsalicylamide and 3-hydroxy-2-naphthoylanilide under the restriction of nanometer cavity of cyclodextrin and cucurbit[8]uril(CB8)was studied experimentally.The substituent effects on the intramolecular proton transfer of the N-(2-hydroxybenzylidene)aniline derivatives was studied by density functional theory.The main work and conclusions are as follows:1.The proton transfer potential functional curve of 3-hydroxy-2-naphthoaclitidine was investigated by density functional method at B3 LYP / 6-31g(d)level,and it was found that intramolecular proton transfer was more likely to happen in the excited state.The fluorescence spectra and transient fluorescence spectra of 3-hydroxy-2-naphthoylanilide in different solvents were measured.The effects of solvent polarity,pH and ?-cyclodextrin on proton transfer of 3-hydroxy-2-naphthoylanilide were investigated.The experimental results show that 3-hydroxy-2-naphthylanilide exhibits double fluorescence in strong polarity solvents such as dimethylsulfoxide(DMSO),N,N-dimethylformamide(DMF)and ethanol.The emission peaks are single fluorescence emission peaks in weak polarity solvents such as ethyl acetate,dichloromethane and cyclohexane.In the ethanol solution of triethylamine,the intensity of the anion emission peak increases with the enhancement of solution basicity.After adding ?-cyclodextrin,the fluorescence intensity was enhanced at the long wave,of the fluorescence lifetime was decreased and the quantum yield was increased.According to Benesi-Hildebrand equation,the stoichiometric ratio of the interaction between the host and guest is 1:1.2.The substituent effects on proton transfer of N-(2-hydroxybenzylidene)aniline derivatives were studied at the B3LYP/6-31+g(d,p)level.The results show that theintroduction of the electron withdrawing group will make the molecules more tending to the planar configuration,and the electron donor will replace the molecules to a certain degree of torsion.After the introduction of the electron-withdrawing substituents,the electron density of the molecular plane is reduced.The N1-H2 distance enhances the intramolecular hydrogen bond strength and reduces the structure of the alcohol to ketone.The electron recombination of the electron donor increases the electron density of the molecular plane,increases the N1-H2 spacing,reduces the intensity of the intramolecular hydrogen bonds,and increases the proton transfer energy barrier.The energy level of the frontier molecular orbits show that the enol tautomer is more likely to form an excited state than the ketone structure,and the energy gap decreases with the increase of the electron-withdrawing ability and the electron-supplying ability.3.The proton transfer potential energy curve of N-phenylsalicylamide was scanned by density functional method at B3LYP/6-316-31+g(d,p)level,and the curves of energy change with H-O distance were obtained.The synthesis and characterization.for N-phenylsalicylamide was also done.The effects of solvent polarity and octane melon ring on the proton transfer of N-phenylsalicylamide were investigated by fluorescence spectroscopy and transient fluorescence spectra in different solvents.The calculation results show that the energy change trend is basically the same both ground state and the excited state,and the energy difference in the excited state is less than the energy difference in the ground state.The experimental results show that the single peak of fluorescence emission spectra is about 450 nm in strong polarity solvents such as dimethylsulfoxide,N,N-dimethylformamide,methanol and acetonitrile.In addition to the peak at 450 nm,a peak appeared at a wavelength of about 350 nm,and a double fluorescence emission peak state was observed in weak polarity solvents such as ethyl acetate,methylene chloride,toluene and cyclohexane.After adding cucurbit[8]uril,the fluorescence intensity showed a tendency to change in cyclohexane and ethyl acetate.Transient spectroscopy indicates that the fluorescence lifetime and quantum yield in cyclohexane and ethyl acetate are a positive correlation with the increase or decrease.By fitting the Benesi-Hildebrand equation,it is found that the stoichiometric ratio of the interaction between the host and guest is 1:2.