Excited State Intramolecular Hydrogen Atom Transfer at Ultralow Temperatures. Evidence for Tunneling and Activated Mechanisms in 1,4-Dimethylanthrone

Gamarnik, Alla; Pang, Lilis; Jenks, William S.

doi:10.1021/ja00105a077

Cited by 19 publications

(26 citation statements)

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“… a Solution time constant in the flow cell are limited by O 2 quenching. b Apparent value shifted to the red due to the interference from high light scattering. c Percentage weighted contribution from a double exponential decay (ref ). d Estimated error, ±0.2 to ±0.4. …”

Section: Results and Discussionmentioning

confidence: 99%

Generation and Reactivity Studies of Diarylmethyl Radical Pairs in Crystalline Tetraarylacetones via Laser Flash Photolysis Using Nanocrystalline Suspensions

et al. 2017

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The nanosecond electronic spectra and kinetics of the radical pairs from various crystalline tetraarylacetones were obtained using transmission laser flash photolysis methods by taking advantage of aqueous nanocrystalline suspensions in the presence of submicellar CTAB, which acts as a surface passivator. After showing that all tetraarylacetones react efficiently by a photodecarbonylation reaction in the crystalline state, we were able to detect the intermediate radical pairs within the ca. 8 ns laser pulse of our laser setup. We showed that the solid-state spectra of the radical pairs are very similar to those detected in solution, with λ in the 330-360 nm range. Kinetics in the solid state was observed to be biexponential and impervious to the presence of oxygen or variations in laser power. A relatively short-lived component (0.3-1.7 μs) accounts for only 3-8% of the total decay with a longer-lived component having a time constant in the range of 40-90 μs depending on the nature of the substituents.

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Section: Results and Discussionmentioning

confidence: 99%

Generation and Reactivity Studies of Diarylmethyl Radical Pairs in Crystalline Tetraarylacetones via Laser Flash Photolysis Using Nanocrystalline Suspensions

et al. 2017

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“…The noteworthy N-demethylation of aclacinomycin A [40] or the oxidation of 1-methylanth~aquinone [41] probably proceeds by mechanistically related photooxidation processes [42]. For the photooxidation of natural rubiginones (OH at C-1) see [5].…”

Section: Electrophilic Substitutionsmentioning

confidence: 99%

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

Krohn

Rohr

1997

Topics in Current Chemistry

182

148

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General and recent aspects of chemical syntheses on angucyclinones and selected related natural products are summarized here. In the first part of this review on angucyclines, the chemical reaction used as a key step for the construction of the angucyclinone frame is discussed. In the second part, new members of the angucycline group of antibiotics, their bioactivity and recent biosynthetic studies including modern aspects of molecular biology (genetics) are reviewed.

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“…1 Large isotope effects and nonlinear Arrhenius plots have been observed, [2][3][4][5] and some theoretical studies have followed. 2,6 It has been proposed that tunneling occurs from n,π* excited states when the transferring hydrogen is favorably positioned relative to the singly occupied n-orbital.…”

Section: Introductionmentioning

confidence: 99%

Deuterium Tunneling in Triplet 5,8-Dimethyl-1-tetralone by Phosphorescence Detection between 80 and 15 K

Johnson

Gamarnik

1996

J. Phys. Chem.

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Phosphorescence measurements with 5,8-dimethyl-1-tetralone (DMT) and 5,8-dimethyl-1-tetralone-d 8 (DMTd 8 ) in methylcyclohexane were carried out between 15 and 80 K to analyze their triplet-state hydrogen-and deuterium-transfer reactions. As expected for a decay process displaying a very large isotope effect, emission could be observed only for the deuterated compound. Phosphorescence intensities and decay measurements in the case of DMT-d 8 were analyzed to determine the rates of deuterium transfer which were used to build an Arrhenius plot where tunneling can be readily identified. A temperature-independent triplet state reaction rate (k D (QMT) ) (5 ( 1) × 10 2 s -1 ) below 40 K was assigned to quantum mechanical tunneling. Detection of the photoproduct after irradiation at 77 and 15 K was accomplished by fluorescence and by FTIR spectroscopy. Results obtained in this study are in excellent agreement with laser flash photolysis results reported by Al-Soufi et al. (Al-Soufi, W.; Grellmann, K. H. J. Phys. Chem. 1991, 95, 2022-2026.

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Excited State Intramolecular Hydrogen Atom Transfer at Ultralow Temperatures. Evidence for Tunneling and Activated Mechanisms in 1,4-Dimethylanthrone

Cited by 19 publications

References 0 publications

Generation and Reactivity Studies of Diarylmethyl Radical Pairs in Crystalline Tetraarylacetones via Laser Flash Photolysis Using Nanocrystalline Suspensions

Generation and Reactivity Studies of Diarylmethyl Radical Pairs in Crystalline Tetraarylacetones via Laser Flash Photolysis Using Nanocrystalline Suspensions

Angucyclines: Total syntheses, new structures, and biosynthetic studies of an emerging new class of antibiotics

Deuterium Tunneling in Triplet 5,8-Dimethyl-1-tetralone by Phosphorescence Detection between 80 and 15 K

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