Chiral, flexible binaphthol-substituted tetrathiafulvalenes
Résumé
Novel chiral tetrathiafulvalene derivatives incorporating one or two binapthol moieties are described where two flexible (Ar-O)-CH2-CH2-S-(TTF) links generate a large 14-membered ring on one or both sides of the TTF core. The symmetric donor molecule with two chiral binaphthol moieties has been prepared as enantiopure (RR) or (SS) isomer, as well as diastereomeric mixture containing the (RR), (SS), and meso (RS)double bond; length as m-dash(SR) forms. Other unsymmetrically substituted derivatives bearing one single chiral binaphthol substituent on one side were also prepared in their enantiopure (R) and (S) forms and as racemic mixture. X-ray crystal structure determinations of different donor molecules show that the TTF tend to associate into face-to-face dyads with a strong folding of the dithiole rings along the S⋯S hinge while the binaphthol moieties adopt a cisoid conformation with a dihedral angle between naphthyl rings in the range 80-85°. The racemic EDT/TTF derivative allowed for the isolation of two crystalline charge-transfer compounds with the electron acceptors TCNQ and TCNQF4. The donor and acceptor molecules are organized into homo-dyads in the TCNQ neutral complex, insulating and diamagnetic. On the other hand, a full charge transfer occurs in the TCNQF4 salt, with weakly interacting chiral TTF cation and TCNQF4 anion radicals.