ESR, UV-Visible and Infrared Spectroscopies of Hexakis(Alkylthio)Benzene Cations with C3Symmetry

Abstract

Abstract The cations of the new series of hexakis(alkylthio)benzenes with C3 symmetry have been studied in solution as well as in solid state. Dications are more stable in acidic medium and the second redox potential appears to be higher than for hexamethoxytriphenylene (HMT). Electronic spectra of monocations show molecular excitation bands without evidence for dimer species. ESR spectra present sometimes an hyperfine structure indicating a mean C3 symmetry. Dications are chemically less stable and we have not been able to detect a triplet state. We suspect that a Jahn-Teller distorsion could cause the dication to have a singlet ground state. In solid state crystals of triethylenedithiobenzene-tetrafluoroborate (tEDT-B)2BF4 have a charge transfer band corresponding to a mixed valence state. The complexation with tetrafluorotetracyanoquinodimethane gives crystals of (tEDT-B)2TCNQF4 which present stacking columns of alternating donor dyads and acceptor monads (DAD units) with an intense charge transfer band at 10 000 cm−1.