  Electrical current rectification is an interesting electronic feature,
popularly known as a diode. Achieving a high rectification ratio in a molecular
junction has been a long-standing goal in molecular electronics. The present
work describes mimicking electrical current rectification with pi-stacked
rhenium(I) compound sandwiched between two electrical contacts. Among the two
mononuclear rhenium compounds studied here, [Re(CO)4(PPh3){(N)-saccharinate}]
(1) and [Re(CO)3(phen){(N)-saccharinate}] (2), the latter show strong pi-pi
interactions-induced high rectification ratio of ~ 4000 at 2.0 V at room
temperature. Alternating current (AC)-based electrical measurements ensuring AC
to DC electrical signal conversion at a frequency f of 1 KHz showing 2 can act
as an excellent half-wave rectifier. Asymmetric charge injection barrier height
at the electrode/Re(I) interfaces of the devices with a stacking configuration
of p++-Si/Re compound31nm(2)/ITO originates the flow of electrical current
unidirectionally. The charge transport mechanism governed by thermally
activated hopping phenomena, and charge carrier propagation is explained
through an energy profile considering the Fermi levels of two electrodes, and
the energy of frontier molecular orbitals, HOMO, and LUMO, confirming
rectification is of a molecular origin. The present work paves the way to
combine different organometallic compounds as circuit elements in
nanoelectronic devices to achieve numerous exciting electronic features.
