Theoretical Investigation Of Photochemical Properties Of Three PRODAN Derivatives Based On Hydrogen Bonding

Photochemical reactions are also known as actinogenesis,which processes are closely related to the origin of life.Since the hydrogen bond can affect the properties on the ground state and the excited state,the dynamic behavior of hydrogen bonds,especially the excited state hydrogen bond kinetic behavior,has attracted much attention.PRODAN(6-propionyl-2-dimethylaminonaphthalene)is a micropolar fluorescent probe with high sensitivity to hydrogen bonding.Aiming at the influence of hydrogen bonds on the molecules of PRODAN derivatives measured in experiments,three kinds of PRODAN derivatives were theoretically calculated under photocatalytic conditions to explore the specific role of hydrogen bonds in their photochemical behavior.(1)For the PRODAN derivative 1a in methanol solution,mainly study the photochemical properties of three different types of intermolecular hydrogen bond complexes PRODAN-1a-MeOH(a),(b),(c)which on the ground and excited states.By analyzing the geometry,excitation energy,frontier molecular orbital and infrared spectra,it was determined that the hydrogen bonds of PRODAN-1a-MeOH(a)and(b)complexes are enhanced after photoexcitation,whereas the intermolecular hydrogen bond of PRODAN-1a-MeOH(c)is relatively weak in the excited state.(2)For the PRODAN derivative 1a in toluene solution,the photochemical properties of the hydrogen bond complex PRODAN-1a-toluene on the excited state were calculated.By analyzing the geometry of the molecules in different electronic states,the electronic excitation energy,the frontier molecular orbitals,electron spectroscopy and hydrogen bonding energy,it was found that the hydrogen bond complex PRODAN-1a-toluene has enhanced intermolecular hydrogen bonding after photoexcitation.(3)For the PRODAN derivative 2b molecule,studied the photochemical behavior on the excited state that of the three hydrogen bond complexes which formed by the monomer and methanol molecule.By analyzing the geometry on the ground state and the first singlet excited state,the electronic spectrum,the frontier molecular orbital and the dipole moment,it is found that with the increase of the concentration of methanol in the hydrogen bond system,the intermolecular hydrogen bonding will also be significantly enhanced after photoexcitation.At the same time,the absorption spectra,fluorescence emission spectra and the infrared spectra of the related groups showed obvious red shifts in the electron excited states.(4)For the PRODAN derivative 3a molecule,the effect of hydrogen bond on the photochemical properties of PRODAN derivative 3a in methanol and toluene solution was studied.The calculation of the physical parameters such as electron excitation energy,oscillator strength,electron spectra and infrared spectra shows that the intermolecular hydrogen bonding of hydrogen bond complexes in both solutions is enhanced after photoexcitation.And the different red shift of the emission spectrum of PRODAN derivative 3a in the two solutions is attributed to the different hydrogen acceptance ability of the solvent molecules.