Pseudo-bimolecular [2+2] cycloaddition studied by time-resolved photoelectron spectroscopy
| Autor: | Vitaly Raev, Albert Stolow, Gary D. Enright, Andrey E. Boguslavskiy, Henning Hopf, Theis I. Sølling, Ditte L. Thomsen, Oliver Schalk, Peter G. Jones, Rasmus Y. Brogaard |
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| Jazyk: | angličtina |
| Rok vydání: | 2011 |
| Předmět: |
Models
Molecular Vinyl Compounds photoelectron spectroscopy Molecular Conformation Photochemistry Catalysis Crystal X-Ray Diffraction X-ray photoelectron spectroscopy Ab initio quantum chemistry methods Polycyclic Compounds Reactivity (chemistry) Conformational isomerism cycloaddition photochemistry Chemistry ab initio calculations Organic Chemistry General Chemistry Conical intersection Cycloaddition Crystallography Cyclization cyclophanes Quantum Theory Ground state |
| Popis: | The first study of pseudo-bi- molecular cycloaddition reaction dy- namics in the gas phase is presented. We used femtosecond time-resolved photoelectron spectroscopy (TRPES) to study the (2+2) photocycloaddition in the model system pseudo-gem- divinylAane. From X- ray crystal diffraction measurements we found that the ground-state mole- cule can exist in two conformers; a re- active one in which the vinyl groups are immediately situated for (2+2) cy- cloaddition and a nonreactive confor- mer in which they point in opposite di- rections. From the measured S1 life- times we assigned a clear relation be- tween the conformation and the excit- ed-state reactivity; the reactive conformer has a lifetime of 13 ps, pop- ulating the ground state through a con- ical intersection leading to (2+2) cyclo- addition, whereas the nonreactive con- former has a lifetime of 400 ps. Ab initio calculations were performed to locate the relevant conical intersection (CI) and calculate an excited-state (2+2) cycloaddition reaction path. The interpretation of the results is support- ed by experimental results on the simi- lar but nonreactive pseudo-para- divinylAane, which has a lifetime of more than 500 ps in the S1 state. |
| Databáze: | OpenAIRE |
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