The Energy Level Structure And Spectral Calculation Of The Melon Ring Molecule

Because of the properties of poor solubility in water,insolubility in organic solvents and soluble in acid solvent of cucurbituril[n](CB[n]),this restricts its application to a great extent.Therefore,the research and synthesis of the modified CB[n] is an important content of its research and application.Based on the full summay of the research results on CB[n] and their derivatives in recent years in this thesis,the research direction and research content are established for calculating the energy level structure and spectral of CB[n].We mainly study on C B[n](n=5~10)in three aspects in this thesis:Firstly,the density functional theory(DFT)is used to optimize the geometrical structure of C B[n](n=5~10)at 6-311g(d)basis level in the gas phase environment.And then the state density function with a unit positive charge and a unit negative charge are calculated.The active sites and chemical stability of C B[n](n=5~10)are analyzed in detail by calculating C B[n](n=5~10)active sites isomorphic surface distribution,condensed Fukui function,condensed dual descriptor,frontier orbit component and concept index of density functional theory(DFT).The results show that the methine H atom is the most active site attacked by the nucleophile,and the carbonyl O atom is the most active site attacked by the electrophilic agent.The reaction activity of CB[n](n=5~10)molecules increases gradually and the chemical stability decreases with n increasing.Secondly,the infrared spectra of CB[n](n=5~10)molecules are calculated in the gas phase.The changes of the absorption peak frequency and absorption peak intensity of ir spectra are matched by the structural changes of the molecular structure of CB[n =5~10].The results show that: 1)The absorption peaks of two vibration modes of ?(?-H)and ?(?-H)of CB[n](n =7,8)are degeneracy;2)The absorption frequency of the stretching vibration ?(?=O)is red shifted.3)The increase of the absorption peak intensity in the vibration mode near the 1200 cm-1 wavenumber is especially noticeable.4)The ring tension of CB[n](n=5~10)gradually decreases with n increasing.Finally,the excited state of CB[n](n=5~10)are calculated by using the timedependent density functional theory(TD-DFT)at the same group level.In the 15 excited states calculated,the UV spectra of CB[n](n=5~10)are mainly determined by two electron transition modes,where the absorption peak of the two transition modes with the largest contribution of the CB[8] UV spectrum is completely coincident.The UV absorption wavelength of the maximum absorption peak of CB[n](n=5~10)increases from 198.8317 nm to 202.2633 nm with n from 5 to 10.Methylene C H2 has an isolation effect in the formation of UV spectra for CB[n](n=5~10).The distribution of electron and hole are symmetry and localized excitation(LE).