Photoswitches Containing a Dithiafulvene Electron Donor

Abstract

Abstract 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.