Unimolecular rectification down to 105 K and spectroscopy of hexadecylquinolinium tricyanoquinodimethanide

We found electrical rectification in a single molecule, gamma-hexadecylquin olinium tricyanoquinomethanide, 1, in which the ground state is zwitterioni c: D+-pi-A(-), while the first excited state is undissociated: D-0-pi-A(0), 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-W, 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. (C) 2000 Elsevier Science S.A. AU rights reserved.