Diarylethene Photoswitches Featuring Tetrathiafulvalene-Containing Aryl Units

The modulation of the electron-donor properties of tetrathiafulvalene (TTF) with light is attempted by two molecular designs: the integration of the TTF core as aryl unit(s) into the hexatriene system of diarylethene (DAE) derivatives and the attachment of terminal TTF unit(s) to a conventional 1,2-dithienylcyclopentene chromophore via conjugated ethynylene spacers. While photochromism is inhibited in the first approach, presumably by a twisted intramolecular charge transfer mechanism, the second approach yields photoswitchable TTF derivatives. Remarkably, the extension of the conjugated π-system upon ring closure affects the first oxidation potential values of the TTF–DAEs only slightly. Nevertheless, the electronic changes in the photochromic core are foreseen to play a crucial role in the intramolecular electron transfer process in donor–DAE–acceptor architectures.