title: The mechanism of excited-state proton transfer in 1-naphthol-piperidine clusters.
abstract: The geometries of 1-naphthol-(piperidine)n (1-NpOH-(Pip)n) (n = 0-3) clusters have been calculated by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods to investigate excited-state proton transfer (ESPT) in the low-lying singlet excited states, La and Lb. For the n = 1 cluster, no PT structure was found in Lb and La as well as the ground state, S0. For n = 2, optically accessible Lb from S0 shows the PT structure. We therefore concluded that the threshold size of ESPT is n = 2, which is consistent with previous experimental results. ESPT in 1-NpOH-(Pip)n is simply triggered by optical excitation to Lb. It is essentially different from the 1-NpOH-(NH3)n cluster in which an internal conversion process is required to promote ESPT. From the calculated structures, the importance of the solvation of the π-ring is strongly suggested rather than the proton affinity in ESPT.
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan. mfujii@res.titech.ac.jp.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Shimizu
authors.forename: Shun
authors.initials: S
authors.lastname: Manita
authors.forename: Shunpei
authors.initials: S
authors.lastname: Yoshikawa
authors.forename: Kenro
authors.initials: K
authors.lastname: Hashimoto
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Miyazaki
authors.forename: Masaaki
authors.initials: M
authors.lastname: Fujii
mesh_terms: D006860:Hydrogen Bonding; D008958:Models, Molecular; D009284:Naphthols / Q000737:chemistry*; D010880:Piperidines / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory
chemical_list: D009284:Naphthols; D010880:Piperidines; D011522:Protons; C029350:1-naphthol; C032727:piperidine