Dihydroazulene-Azobenzene-Dihydroazulene Triad Photoswitches
Creators
- 1. Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
- 2. LENS, via N. Carrara1, 50019 Sesto Fiorentino (FI), Italy
- 3. Department of Chemistry "U. Schiff", University of Florence, via della Lastruccia 3-13, 50019 Sesto Fiorentino (FI), Italy
Description
Photoswitch triads comprised of two dihydroazulene (DHA) units in conjugation to a central trans-azobenzene (AZB) unit were prepared in stepwise protocols starting from meta- and paradisubstituted azobenzenes. The para-connected triad had significantly altered optical properties and lacked the photoactivity of the separate photochromes. Instead, for the meta-connected triad all three photochromes could be photoisomerized to generate an isomer with two vinylheptafulvene (VHF) units and a cis-azobenzene unit. The photoisomerizations were studied by ultrafast spectroscopy, revealing a fast DHA-to-VHF photoisomerization and a slower trans-to-cis AZB photoisomerization. This meta triad underwent thermal VHF-to-DHA back-conversions with a similar rate of all VHFs, independent of the identity of the neighboring units, and in parallel thermal cis-to-trans AZB conversion. The experimental observations were supported by computations (excitation spectra and orbital analysis of the transitions).
Files
Mengots_2021_10.1002-chem.202101533.pdf
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