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.