Unimolecular rectification down to 105 K and spectroscopy of hexadecylquinolinium tricyanoquinodimethanide

We found electrical rectification in a single molecule, γ-hexadecylquinolinium tricyanoquinomethanide, 1, in which the ground state is zwitterionic: D+-π-A−, while the first excited state is undissociated: D0-π-A0, between 370 K and 105 K. While the ground state has a high dipole moment (43±8 Debyes), the first excited state has a very low estimated moment, between 3 and 9 Debyes. Spectroscopic measurements (V-UV, FTIR, XPS) confirm this interpretation. The 1974 proposal by Aviram and Ratner [A. Aviram, M.A. Ratner, Chem. Phys. Lett. 29 (1974) 277.] for unimolecular rectification has been confirmed.