Intramolecular Proton Transfer and Tunnel Effects in the Metastable Triplet States of 2-(2’-hydroxyphenyl)benzoxazole Studied by Micro- and Nanosecond Laser Flash Photolysis
نویسندگان
چکیده
The enol-keto tautomerism of 2-(2’-hydrophenyl)benzoxazole (HBO) in its metastable triplet states has been studied in fluid, non-polar solution. After laser flash excitation the keto triplet state is populated with high efficiency. The establishment of a ketoenol equilibrium was observed between 55 and 220 K. At low temperatures the rate of this reaction is determined by tunnel effects. The barrier height of the proton transfer is in the triplet state much larger than in the singlet state.
منابع مشابه
Mechanistic Studies of Photoinitiated Free Radical Polymerization Using a Bifunctional Thioxanthone Acetic Acid Derivative as Photoinitiator
A bifunctional photoinitiator for free radical polymerization, thioxanthone catechol-O,O0diacetic acid, was synthesized, characterized, and compared to photoinitiator parameters of the monofunctional analogue, 2-(carboxymethoxy)thioxanthone. Photophysical studies such as fluorescence, phosphorescence, and laser flash photolysis in addition to photopolymerizations of methyl methacrylate show tha...
متن کاملPhotochemical & Photobiological Sciences Paper 2-hydroxyphenacyl Ester: a New Photoremovable Protecting Group † ‡
A 2-hydroxyphenacyl moiety absorbing below 370 nm is proposed as a new photoremovable protecting group for carboxylates and sulfonates. Laser flash photolysis and steady-state sensitization studies show that the leaving group is released from a short-lived triplet state. In addition, DFT-based quantum chemical calculations were performed to determine the key reaction steps. We found that triple...
متن کاملEffect of beta-alkylthioethyl substitution in 1,3-dithianes: quasianchimeric assistance in photoinduced electron transfer?
Nanosecond laser flash photolysis (LFP) experiments show that the rates of ET quenching of triplet benzophenone by 2-alkyldithianes significantly decrease with bulkier substitution. Introduction of sulfur at the beta-position of the flexible alkyl chain reverses this trend, whereas such substitution at the alpha-position has negligible effect. This is rationalized in terms of the three electron...
متن کامل2-Hydroxyphenacyl ester: a new photoremovable protecting group.
A 2-hydroxyphenacyl moiety absorbing below 370 nm is proposed as a new photoremovable protecting group for carboxylates and sulfonates. Laser flash photolysis and steady-state sensitization studies show that the leaving group is released from a short-lived triplet state. In addition, DFT-based quantum chemical calculations were performed to determine the key reaction steps. We found that triple...
متن کاملCyclotriphosphazene appended porphyrins and fulleropyrrolidine complexes as supramolecular multiple photosynthetic reaction centers: steady and excited states photophysical investigation.
New multiple photosynthetic reaction centers were constructed from cyclophosphazene decorated multiporphyrin chromophores and a fulleropyrrolidine having a pyridine ligand (FPY). The excited state electron transfer in the self-assembled donor-acceptor assembly was investigated by using steady state absorption and emission, time-resolved emission spectroscopy and nanosecond laser flash photolysi...
متن کامل