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Molecular mechanisms of the photostability of indigo
| Title: | Molecular mechanisms of the photostability of indigo |
| Authors: | Yamazaki, Shohei Browse this author | | Sobolewski, Andrzej L. Browse this author | | Domcke, Wolfgang Browse this author |
| Issue Date: | 28-Jan-2011 |
| Publisher: | Royal Society of Chemistry |
| Journal Title: | Physical Chemistry Chemical Physics |
| Volume: | 13 |
| Issue: | 4 |
| Start Page: | 1618 |
| End Page: | 1628 |
| Publisher DOI: | 10.1039/c0cp01901a |
| PMID: | 21152507 |
| Abstract: | The photophysics of indigo as well as of bispyrroleindigo, the basic chromophore of indigo, has been investigated with ab initio electronic-structure calculations. Vertical electronic excitation energies and excited-state potential-energy profiles have been calculated with the CASSCF, CASPT2 and CC2 methods. The calculations reveal that indigo and bispyrroleindigo undergo intramolecular single-proton transfer between adjacent N-H and C=O groups in the 1ππ* excited state. The nearly barrierless proton transfer provides the pathway for a very efficient deactivation of the 1ππ* state via a conical intersection with the ground state. While a low-lying S1-S0 conical intersection exists also after double-proton transfer, the latter reaction path exhibits a much higher barrier. The reaction path for trans → cis photoisomerization via the twisting of the central C=C bond has been investigated for bispyrroleindigo. It has been found that the twisting of the central C=C bond is unlikely to play a role in the photochemistry of indigo, because of a large potential-energy barrier and a rather high energy of the S1-S0 conical intersection of twisted structure. These findings indicate that the exceptional photostability of indigo is the result of rapid internal conversion via intramolecular single-proton transfer, combined with the absence of a low-barrier reaction path for the generation of the cis isomer via trans → cis photoisomerization. |
| Rights: | Phys. Chem. Chem. Phys., 2011, 13, 1618-1628 - Reproduced by permission of the PCCP Owner Societies |
| Type: | article (author version) |
| URI: | http://hdl.handle.net/2115/47361 |
| Appears in Collections: | 理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)
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Submitter: 山崎 祥平
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