Isotope and temperature effects in ultrafast proton‐transfer from a strong excited‐state acid

Pines, Ehud; Pines, Dina; Barak, Tamar; Magnes, Ben‐Zion; Tolbert, Laren M.; Haubrich, Jeanne E.

doi:10.1002/bbpc.19981020334

Cited by 72 publications

(105 citation statements)

References 22 publications

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“…By assuming that the isotope effect for m-ANCN has the same magnitude with that for AN, the k dis value of m-ANCN in H 2 O was estimated to be 3.7 Â 10 11 s À1 . It can be found from this result that the proton-dissociation time (2.7 ps) of m-ANCN in H 2 O is shorter than that (8 ps) of 5-cyano-1-naphthol [25] which is fastest photoacid dissociation time in water reported so far. The k dis values obtained in the present study are summarized in Table 2.…”

Section: Proton-dissociation Rate Of Aniline Derivativesmentioning

confidence: 48%

Substituent effects on ultrafast excited-state proton transfer of protonated aniline derivatives in aqueous solution

Shiobara¹,

Tajima²,

Tobita³

2003

Chemical Physics Letters

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Section: Proton-dissociation Rate Of Aniline Derivativesmentioning

confidence: 48%

Substituent effects on ultrafast excited-state proton transfer of protonated aniline derivatives in aqueous solution

Shiobara¹,

Tajima²,

Tobita³

2003

Chemical Physics Letters

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“…The same general dependence on alcohol structure as has been observed in previous work with carbenes in which the most rapid protonation occurs in methanol with other primary, secondary, and tertiary alcohols protonating at slower rates that are similar to each other 33a,b. The protonation of the nitrene by methanol observed in this work ranks with the fastest intermolecular proton transfer processes known, which includes the protonation of singlet diphenylcarbene by methanol, τ = 9 ps,33a,b and the protonation of water by several excited photoacids 34a,b…”

Section: Resultsmentioning

confidence: 68%

Photoaffinity Labeling via Nitrenium Ion Chemistry: Protonation of the Nitrene Derived from 4-Amino-3-nitrophenyl Azide to Afford Reactive Nitrenium Ion Pairs

et al. 2009

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Phenyl azides with powerful electron-donating substituents are known to deviate from the usual photochemical behavior of other phenyl azides. They do not undergo ring expansion, but form basic nitrenes that protonate to form nitrenium ions. The photochemistry of the widely used photoaffinity labeling system 4-amino-3-nitrophenyl azide, 5, has been studied by transient absorption spectroscopy from femtosecond to microsecond time domains and from a theoretical perspective. The nitrene generation from azide 5 occurs on the S 2 surface, in violation of Kasha's rule. The resulting nitrene is a powerful base and abstracts protons extremely rapidly from a variety of sources to form a nitrenium ion. In methanol, this protonation occurs in about 5 ps, which is the fastest intermolecular protonation observed to date. Suitable proton sources include alcohols, amine salts, and even acidic C-H bonds such as acetonitrile. The resulting nitrenium ion is stabilized by the electron-donating 4-amino group to afford a diiminoquinone-like species that collapses relatively slowly to form the ultimate cross-linked product. In some cases in which the anion is a good hydride donor, cross-linking is replaced by reduction of the nitrenium ion to the corresponding amine.

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“…14,18,19 It may be depicted schematically by the following scheme In this mechanism, the initial state is that of a vibrationally relaxed, electronically excited ROH molecule (denoted by R*OH). It may dissociate to produce a "contact" geminate pair with a rate coefficient k d .…”

Section: Introductionmentioning

confidence: 99%

Photochemistry of “Super”-Photoacids. Solvent Effects

1999

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We study steady-state and time-resolved fluorescence of 5-cyano-2-naphthol in various pure solvents. To some of these, excited-state proton transfer occurs within the excited-state lifetime of the chromophore. Solvatochromic shifts in the acid and anion bands are analyzed using the empirical Kamlet-Taft approach. The hydrogen-bond donated from the OH group to basic solvents accounts for most of the shift in the excitation spectra. This bond produces considerably larger shifts in the emission spectra, suggesting that it strengthens in the excited state. In contrast, the hydrogen bond donated from protic solvents to the hydroxyl oxygen is cleaved following photoexcitation. This bond (and not the change in dielectric constant) is responsible for the solvent-induced blue shift in anion fluorescence. Hence it must re-form simultaneously with the protontransfer event. Our time-resolved fluorescence data fit the solution of the Debye-Smoluchowski equation for reversible geminate recombination in a field of force, provided that the difference in excited-state lifetimes and contact quenching are taken into account. An extended theory of reversible geminate recombination provides an accurate description of the asymptotic behavior in this case. The quenching processes correlate with the solvent hydrogen-bond donation ability, implicating the involvement of hydrogen-bonded pathways.

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Isotope and temperature effects in ultrafast proton‐transfer from a strong excited‐state acid

Cited by 72 publications

References 22 publications

Substituent effects on ultrafast excited-state proton transfer of protonated aniline derivatives in aqueous solution

Substituent effects on ultrafast excited-state proton transfer of protonated aniline derivatives in aqueous solution

Photoaffinity Labeling via Nitrenium Ion Chemistry: Protonation of the Nitrene Derived from 4-Amino-3-nitrophenyl Azide to Afford Reactive Nitrenium Ion Pairs

Photochemistry of “Super”-Photoacids. Solvent Effects

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