title: Multiple hydrogen bonding in excited states of aminopyrazine in methanol solution: time-dependent density functional theory study.
abstract: Aminopyrazine (AP) and AP-methanol complexes have been theoretically studied by using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The excited-state hydrogen bonds are discussed in detail. In the ground state the intermolecular multiple hydrogen bonds can be formed between AP molecule and protic solvents. The AP monomer and hydrogen-bonded complex of AP with one methanol are photoexcited initially to the S2 state, and then transferred to the S1 state via internal conversion. However the complex of AP with two methanol molecules is directly excited to the S1 state. From the calculated electronic excited energies and simulated absorption spectra, we find that the intermolecular hydrogen bonds are strengthened in the electronic excited states. The strengthening is confirmed by the optimized excited-state geometries. The photochemical processes in the electronic excited states are significantly influenced by the excited-state hydrogen bond strengthening.
authors.affiliation: School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Shuo
authors.initials: S
authors.lastname: Chai
authors.forename: Jie
authors.initials: J
authors.lastname: Yu
authors.forename: Yong-Chang
authors.initials: YC
authors.lastname: Han
authors.forename: Shu-Lin
authors.initials: SL
authors.lastname: Cong
mesh_terms: D003198:Computer Simulation; D004583:Electrons; D005453:Fluorescence; D006860:Hydrogen Bonding; D008027:Light; D000432:Methanol / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011719:Pyrazines / Q000737:chemistry*; D011789:Quantum Theory; D012996:Solutions; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D011719:Pyrazines; D012996:Solutions; C079424:2-aminopyrazine; D000432:Methanol
keywords: Electronic excited state; Hydrogen bond strengthening; Internal conversion; Time-dependent density functional theory