Photoswitches Containing a Dithiafulvene Electron Donor


  • The Danish Research Agency (grant #2111-04-0018) is acknowledged for financial support. We thank the laboratory technician Niels Vissing Holst for help with sample preparation and spectroscopic measurements.


Three new chromophores containing an electron-donating dithiafulvene (DTF) unit attached to derivatives of retinal, diethynylethene (DEE), and dihydroazulene (DHA), respectively, are synthesized and characterized by using X-ray crystallography as well as absorption and fluorescence spectroscopy. In general, the DTF unit induces a significant red-shift in the lowest-energy absorption in all investigated chromophores. The influence of the DTF unit on light-induced cis–trans isomerization and on retro-electrocyclization is investigated. Although the retinylidene derivative decomposes when subjected to light, the DTF-functionalized DEE and DHA compounds undergo reversible isomerization. Computations show that the highest occupied molecular orbital (HOMO) of DTF–DHA is spread over most of the π-conjugated system, whereas it is more localized in the ring-opened product. This difference is reflected in the redox properties.