Acetylenic Tetrathiafulvalene Scaffolds - Intramolecular Charge-Transfer Molecules

Two tetrathiafulvalene-functionalized acetylenic scaffolds were synthesized by Glaser-Hay and Sonogashira coupling reactions; the one scaffold was based on a central dehydroannulene core and the other on a tetraethynylethene core. Peripheral propyl groups on the tetrathiafulvalenes ascertained solubility. The compounds are strong donor-acceptor chromophores and exhibit characteristic charge-transfer absorptions according to UV/VIS absorption spectroscopy. Furthermore, the redox properties were investigated by cyclic and differential-pulse voltammetries. The experiments allow for a direct comparison between the acceptor strengths of the two acetylenic cores, and the conclusions are supported by electron-affinity calculations.