Asymmetries in the macroscopic and the nanoscopic DC electrical conductivity through Langmuir–Blodgett multilayers and monolayers of γ‐(n‐hexadecyl)quinolinium tricyanoquinodimethanide (HDQ‐3CNQ, 1) are due to a transition from the ground‐state zwitterion to a probably neutral excited‐state conformer, thus confirming without a shadow of a doubt the rectification of electrical current by a single molecule. © 1998 John Wiley & Sons, Ltd.