Shedding Light on the Photoisomerization Pathway of Donor-Acceptor Stenhouse Adducts

Mariangela Di Donato, Michael M. Lerch, Andrea Lapini, Adèle D. Laurent, Alessandro Iagatti, Laura Bussotti, Svante P. Ihrig, Miroslav Medved, Denis Jacquemin, Wiktor Szymanski, Wybren Jan Buma, Paolo Foggi, Ben L. Feringa*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Donor-acceptor Stenhouse adducts (DASAs) are negative photochromes that hold great promise for a variety of applications. Key to optimizing their switching properties is a detailed understanding of the photoswitching mechanism, which, as yet, is absent. Here we characterize the actinic step of DASA-photoswitching and its key intermediate, which was studied using a combination of ultrafast visible and IR pump-probe spectroscopies and TD-DFT calculations. Comparison of the time-resolved IR spectra with DFT computations allowed to unambiguously identify the structure of the intermediate, confirming that light absorption induces a sequential reaction path in which a Z-E photoisomerization of C-2-C-3 is followed by a rotation around C-3-C-4 and a subsequent thermal cyclization step. First and second-generation DASAs share a common photoisomerization mechanism in chlorinated solvents with notable differences in kinetics and lifetimes of the excited states. The photogenerated intermediate of the second-generation DASA was photo-accumulated at low temperature and probed with time-resolved spectroscopy, demonstrating the photoreversibility of the isomerization process. Taken together, these results provide a detailed picture of the DASA isomerization pathway on a molecular level.

Original languageEnglish
Pages (from-to)15596-15599
Number of pages4
JournalJournal of the American Chemical Society
Volume139
Issue number44
DOIs
Publication statusPublished - 8-Nov-2017

Keywords

  • VISIBLE-LIGHT
  • INFRARED-SPECTROSCOPY
  • RESPONSIVE POLYMER
  • MOLECULAR SWITCHES
  • PHOTOPHARMACOLOGY
  • ISOMERIZATION
  • PHOTOSWITCHES
  • SPECTRA
  • SYSTEM

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