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Electron–Proton Decoupling in Excited‐State Hydrogen Atom Transfer in the Gas Phase
Author(s) -
Miyazaki Mitsuhiko,
Ohara Ryuhei,
Daigoku Kota,
Hashimoto Kenro,
Woodward Jonathan R.,
Dedonder Claude,
Jouvet Christophe,
Fujii Masaaki
Publication year - 2015
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201506467
Subject(s) - photoexcitation , chemistry , photochemistry , electron transfer , excited state , proton coupled electron transfer , hydrogen atom , photodissociation , picosecond , proton , intramolecular force , flash photolysis , atomic physics , stereochemistry , kinetics , reaction rate constant , laser , quantum mechanics , physics , alkyl , organic chemistry , optics
Hydrogen‐release by photoexcitation, excited‐state‐hydrogen‐transfer (ESHT), is one of the important photochemical processes that occur in aromatic acids and is responsible for photoprotection of biomolecules. The mechanism is described by conversion of the initial state to a charge‐separated state along the O(N)‐H bond elongation, leading to dissociation. Thus ESHT is not a simple H‐atom transfer in which a proton and a 1s electron move together. Here we show that the electron‐transfer and the proton‐motion are decoupled in gas‐phase ESHT. We monitor electron and proton transfer independently by picosecond time‐resolved near‐infrared and infrared spectroscopy for isolated phenol–(ammonia) 5 , a benchmark molecular cluster. Electron transfer from phenol to ammonia occurred in less than 3 picoseconds, while the overall H‐atom transfer took 15 picoseconds. The observed electron‐proton decoupling will allow for a deeper understanding and control of of photochemistry in biomolecules.