Theoretical Study On The Excited State Properties Of One Dye Molecule And Antibiotic Molecules

Photochemistry is made up of photophysical process and photochemical reaction. Especially, the electronic excited state is necessary for all the photochemical reactions as well as photophysical processes. When the molecule in ground sate is excited by light, the electron will transfer between molecule orbitals. At the same time, some of properties of excited states such as geometric configuration, charge distribution, polarity and dipole moment of the molecule come to change. Therefore, it is very important for understanding modern photochemistry to study the molecular structure and electronic properties in the electronic excited states. In this paper, based on density functional theory and time-dependent density functional theory, it provides geometry and related properties for hydrogen-bonded complexes by Gaussian09 program package.Firstly, we researched excited state properties of hydrogen-bonded PNPP-TBA complex with CAM-B3LYP functional,6-311++G (d,p) basis set and CPCM model of dicholoro-ethane. Comparing length and binding energy of hydrogen bond as well as infrared spectrum in different electronic states, we found out that a highly elongated N-H+ bond occurs in excited state. Simultaneously, we could draw a conclusion that S1 is the main and local excited state by comparing electronic excitation energies and oscillator strengths. S1 is confirmed as intramolecular charge-transfer excited state with n-n* transition type by analyzing frontier molecular orbitals and Nature Bond Orbitals.And then, we researched excited properties of hydrogen-bonded CTC-H2O complex with B3LYP functional,6-311++G (d,p) basis set and CPCM model of water. Comparing length and binding energy of hydrogen bond as well as infrared spectrum in different electronic states, we found out that hydrogen bond is enhanced in excited state. Simultaneously, we could draw a conclusion that S2 is the main excited state as well as S1 and S2 are both local excited states by comparing electronic excitation energies and oscillator strengths. S1 and S2 are both confirmed as intramolecular charge-transfer excited state, while only the former possesses π-π* transition type, by analyzing frontier molecular orbitals and NBOs.At last, we researched excited properties of hydrogen-bonded NOR complex with B3LYP functional,6-311++G (d,p) basis set and CPCM model of water. Comparing hydrogen bond length as well as infrared spectrum in different electronic states, we found out that hydrogen bond is enhanced in excited state and that in S4 is stronger than in Si.Simultaneously, we could draw a conclusion that S1, S2, S4 and S6 are all the main excited states by comparing electronic excitation energy and oscillator strengths. S1 and S4 are both confirmed to be π-π* transition type, and S1 is twisted intramolecular charge-transfer excited state, by analyzing frontier molecular orbitals and NBOs.