  Achieving highly transmitting molecular junctions through resonant transport
at low bias is key to the next-generation low-power molecular devices.
Although, resonant transport in molecular junctions was observed by connecting
a molecule between the metal electrodes via chemical anchors by applying a high
source-drain bias (> 1V), the conductance was limited to < 0.1 G$_0$, G$_0$
being the quantum of conductance. Here, we report electronic transport
measurements by directly connecting a Ferrocene molecule between Au electrodes
at the ambient condition in a mechanically controllable break junction setup
(MCBJ), revealing a conductance peak at ~ 0.2 G$_0$ in the conductance
histogram. A similar experiment was repeated for Ferrocene terminated with
amine (-NH2) and cyano (-CN) anchors, where conductance histograms exhibit an
extended low conductance feature including the sharp high conductance peak,
similar to pristine ferrocene. Statistical analysis of the data along with
density functional theory-based transport calculation suggests the possible
molecular conformation with a strong hybridization between the Au electrodes
and Fe atom of Ferrocene molecule is responsible for a near-perfect
transmission in the vicinity of the Fermi energy, leading to the resonant
transport at a small applied bias (< 0.5V). Moreover, calculations including
Van der Waals/dispersion corrections reveal a covalent like organometallic
bonding between Au and the central Fe atom of Ferrocene, having bond energies
of ~ 660 meV. Overall, our study not only demonstrates the realization of an
air-stable highly transmitting molecular junction, but also provides an
important insight about the nature of chemical bonding at the
metal/organo-metallic interface.
