Dihydroazulene‐Azobenzene‐Dihydroazulene Triad Photoswitches

Photoswitch triads comprising two dihydroazulene (DHA) units in conjugation with a central trans-azobenzene (AZB) unit were prepared stepwise protocols starting from meta- and para-disubstituted azobenzenes. The para-connected triad had significantly altered optical properties lacked the photoactivity of separate photochromes. In contrast, for meta-connected triad, all three photochromes could be photoisomerized to generate an isomer vinylheptafulvene (VHF) cis-azobenzene unit. Ultrafast spectroscopy photoisomerizations revealed fast DHA-to-VHF photoisomerization slower trans-to-cis AZB photoisomerization. This meta underwent thermal VHF-to-DHA back-conversion similar rate VHFs, independent identity neighboring units, parallel cis-to-trans conversion. experimental observations supported by computation (excitation spectra orbital analysis transitions).