New Chiral Binaphthyl Building Blocks: Synthesis of the First Optically Active Tetrathiafulvalene and 11,11,12,12-Tetracyano-9,10-anthraquinodimethane Dimers

Abstract

New enantiomerically pure binaphthyl derivatives bearing triphenylphosphine or phosphonate groups have been synthesized and used as building blocks to prepare the first optically active TTF and TCAQ dimers. Due to the restricted rotation of the two naphthalene rings, binaphthyl derivatives are ideal candidates to be used as nonplanar spacers between electroactive units in the search for materials with enhanced dimensionality. The electronic absorption spectra of dimers in which the electroactive unit is in conjugation with the naphthalene fragment reveal the presence of intramolecular photoinduced electron-transfer process from the TTF to the naphthalene unit in 5 and 6 and from the naphthalene moiety to the TCAQ unit in 7. Electrochemical studies on the new dimers show the redox potentials of TTF and TCAQ units as well as the oxidation wave for the naphthalene moiety and reveal no significant electronic interaction between the two electroactive units, which is in agreement with the results obtained from theoretical calculations at the PM-3 level which indicate that the angle between rings in the binaphthyl systems ranges from 75 to 80 degrees.