Synthesis and properties of conjugated hybrid tetrathiafulvalene dimers

The synthesis of new hybrid tetrathiafulvalene (TTF) dimers (11a-c) has bee n carried out by a Wittig-Horner reaction of the respective phosphonate est ers (10a-c) with 2-(tetrathiafulvalenylvinyl)-9,10-anthraquinone (9) prepar ed by olefination of formyltetrathiafulvalene (7) and the phosphonium salt of anthraquinone 8. Electrochemical studies show that the dimers 11a-c main ly retain the electrochemical properties of both TTF and the pi-extended TT F components, and most importantly, intramolecular electronic interactions between the two moieties are observed by cyclic voltammetry and Osteryoung square wave voltammetry. Semiempirical PM3 calculations reveal an almost pl anar geometry for the TTF and the benzene ring connected through the vinyl spacer. These compounds can form stable charge-transfer complexes with 2,3- dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) showing a stoichiometry of 1:3 (D:A). Attempts to electrocrystallize the dimeric donors with different cou nteranions are discussed.