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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Paul, Jared J. Papanikolas, John M. Meyer, Thomas J. Forbes, Malcolm D. E. Miller, Stephen A. Hampton, Shaun D. Brennaman, M. Kyle Bettis, Stephanie E. Westlake, Brittany C. Concepcion, Javier J. Lebedeva, Natalia V. Moran, Andrew M. |
| Description | Author Affiliation: Westlake BC ( Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.); |
| Abstract | The simultaneous, concerted transfer of electrons and protons--electron-proton transfer (EPT)--is an important mechanism utilized in chemistry and biology to avoid high energy intermediates. There are many examples of thermally activated EPT in ground-state reactions and in excited states following photoexcitation and thermal relaxation. Here we report application of ultrafast excitation with absorption and Raman monitoring to detect a photochemically driven EPT process (photo-EPT). In this process, both electrons and protons are transferred during the absorption of a photon. Photo-EPT is induced by intramolecular charge-transfer (ICT) excitation of hydrogen-bonded-base adducts with either a coumarin dye or 4-nitro-4'-biphenylphenol. Femtosecond transient absorption spectral measurements following ICT excitation reveal the appearance of two spectroscopically distinct states having different dynamical signatures. One of these states corresponds to a conventional ICT excited state in which the transferring H(+) is initially associated with the proton donor. Proton transfer to the base (B) then occurs on the picosecond time scale. The other state is an ICT-EPT photoproduct. Upon excitation it forms initially in the nuclear configuration of the ground state by application of the Franck-Condon principle. However, due to the change in electronic configuration induced by the transition, excitation is accompanied by proton transfer with the protonated base formed with a highly elongated (+)H â B bond. Coherent Raman spectroscopy confirms the presence of a vibrational mode corresponding to the protonated base in the optically prepared state. |
| ISSN | 00278424 |
| e-ISSN | 10916490 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Issue Number | 21 |
| Volume Number | 108 |
| Language | English |
| Publisher | National Academy of Sciences |
| Publisher Date | 2011-05-01 |
| Publisher Place | United States |
| Access Restriction | Open |
| Subject Keyword | Coloring Agents Chemistry Electrons Hydrogen Bonding Protons Biphenyl Compounds Coumarins Nitrophenols Photochemical Processes Spectrum Analysis Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Multidisciplinary |
| Content Type | Text |
| Resource Type | Article |
| Subject | Multidisciplinary |
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