Chiral, flexible binaphthol-substituted tetrathiafulvalenes

Abstract

Novel chiral tetrathiafulvalene derivatives incorporating one or two binapthol moieties are described where two flexible (Ar–O)–CH 2–CH 2–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) ( 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 TCNQF 4. 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 TCNQF 4 salt, with weakly interacting chiral TTF cation and TCNQF 4 anion radicals.