title: Time-dependent density functional theory study on the electronic excited-state hydrogen bonding of the chromophore coumarin 153 in a room-temperature ionic liquid.
abstract: In the present work, in order to investigate the electronic excited-state intermolecular hydrogen bonding between the chromophore coumarin 153 (C153) and the room-temperature ionic liquid N,N-dimethylethanolammonium formate (DAF), both the geometric structures and the infrared spectra of the hydrogen-bonded complex C153-DAF(+) in the excited state were studied by a time-dependent density functional theory (TDDFT) method. We theoretically demonstrated that the intermolecular hydrogen bond C(1) = O(1)···H(1)-O(3) in the hydrogen-bonded C153-DAF(+) complex is significantly strengthened in the S(1) state by monitoring the spectral shifts of the C=O group and O-H group involved in the hydrogen bond C(1) = O(1)···H(1)-O(3). Moreover, the length of the hydrogen bond C(1) = O(1)···H(1)-O(3) between the oxygen atom and hydrogen atom decreased from 1.693 Å to 1.633 Å upon photoexcitation. This was also confirmed by the increase in the hydrogen-bond binding energy from 69.92 kJ mol(-1) in the ground state to 90.17 kJ mol(-1) in the excited state. Thus, the excited-state hydrogen-bond strengthening of the coumarin chromophore in an ionic liquid has been demonstrated theoretically for the first time.
authors.affiliation: State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Wang
authors.forename: Ce
authors.initials: C
authors.lastname: Hao
authors.forename: Se
authors.initials: S
authors.lastname: Wang
authors.forename: Hong
authors.initials: H
authors.lastname: Dong
authors.forename: Jieshan
authors.initials: J
authors.lastname: Qiu
mesh_terms: D003374:Coumarins / Q000737:chemistry*; D004583:Electrons; D006860:Hydrogen Bonding; D052578:Ionic Liquids / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D003374:Coumarins; D052578:Ionic Liquids; C488877:coumarin 153