Dihydroazulene-Azobenzene-Dihydroazulene Triad Photoswitches.

Authors :: Mengots A
Erbs Hillers-Bendtsen A
Doria S
Ørsted Kjeldal F
Machholdt Høyer N
Ugleholdt Petersen A
Mikkelsen KV
Di Donato M
Cacciarini M
Brøndsted Nielsen M
Source :: Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2021 Aug 25; Vol. 27 (48), pp. 12437-12446. Date of Electronic Publication: 2021 Jul 06.
Publication Year :: 2021
Abstract: Photoswitch triads comprising two dihydroazulene (DHA) units in conjugation with a central trans-azobenzene (AZB) unit were prepared in stepwise protocols starting from meta- and para-disubstituted azobenzenes. The para-connected triad had significantly altered optical properties and lacked the photoactivity of the separate photochromes. In contrast, 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. Ultrafast spectroscopy of the photoisomerizations revealed a fast DHA-to-VHF photoisomerization and a slower trans-to-cis AZB photoisomerization. This meta triad underwent thermal VHF-to-DHA back-conversion 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 computation (excitation spectra and orbital analysis of the transitions).<br /> (© 2021 Wiley-VCH GmbH.)