Pseudo-bimolecular [2+2] cycloaddition studied by time-resolved photoelectron spectroscopy

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DOIResolve DOI: http://doi.org/10.1002/chem.201002928
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TypeArticle
Journal titleChemistry A European Journal
Volume17
Issue14
Pages39223931; # of pages: 10
Subjectab initio calculations; cycloaddition; cyclophanes; photochemistry; photoelectron spectroscopy
AbstractThe first study of pseudo-bimolecular cycloaddition reaction dynamics 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-divinyl[2.2]paracyclophane. From X-ray crystal diffraction measurements we found that the ground-state molecule can exist in two conformers; a reactive one in which the vinyl groups are immediately situated for [2+2] cycloaddition and a nonreactive conformer in which they point in opposite directions. From the measured S1 lifetimes we assigned a clear relation between the conformation and the excited-state reactivity; the reactive conformer has a lifetime of 13 ps, populating the ground state through a conical intersection leading to [2+2] cycloaddition, whereas the nonreactive conformer 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 supported by experimental results on the similar but nonreactive pseudo-para-divinyl[2.2]paracyclophane, which has a lifetime of more than 500 ps in the S1 state.
Publication date
LanguageEnglish
AffiliationNRC Steacie Institute for Molecular Sciences; National Research Council Canada
Peer reviewedYes
NPARC number19739648
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Record identifier3c7d1236-3de3-4969-b8c8-379ce9ac221e
Record created2012-04-02
Record modified2016-05-09
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