Rectifying Electron-Transport Properties through Stacks of Aromatic Molecules Inserted into a Self-Assembled Cage

Aromatic stacks formed through self-assembly
are promising building blocks for the construction of
molecular electronic devices with adjustable electronic
functions, in which noncovalently bound π-stacks act as
replaceable modular components. Here we describe the
electron-transport properties of single-molecule aromatic
stacks aligned in a self-assembled cage, using scanning probe
microscopic and break junction methods. Same and different
modular aromatic pairs are noncovalently bound and stacked within the molecular cage holder, which leads to diverse electronic functions. The insertion of same pairs induces high electronic conductivity (10−3−10−2 G0, G0 = 2e2/h), while different pairs develop additional electronic rectification properties. The rectification ratio was, respectively, estimated to be 1.4−2 and >10 in current−voltage characteristics and molecular orientation-dependent conductance measurements at a fixed bias voltage. Theoretical calculations demonstrate that this rectification behavior originates from the distinct stacking order of the internal aromatic components against the electron-transport direction and the corresponding lowest unoccupied molecular orbital conduction channels localized on one side of the molecular junctions.