Conductance of Single 1,4-Benzenediamine Molecule Bridging between Au and Pt Electrodes

We investigated the single 1,4-benzenediamine molecule bridging between Au or Pt electrodes. The conductances of the molecular junctions with the Au−NH 2 and Pt−NH 2 bonds (Au−NH 2 and Pt−NH 2 molecular junctions) were 1 × 10 −2 G 0 (2 e 2 / h ) and 5 × 10 −3 G 0, respectively. The stretching lengths of the Au−NH 2 and Pt−NH 2 molecular junctions were 0.03 and 0.07 nm, respectively. The conductance value of the Au−NH 2 molecular junction was unexpectedly larger than the value evaluated with the density of states of the metal electrodes and the molecule−metal bond strength, which have been discussed before. The large conductance value could be explained by the small energy difference between metal and molecular orbitals (Δ E ) and the high degree of π-conjugation ( P ) of the Au−NH 2 molecular junction, which would be unique characteristics of the Au−NH 2 bond. The present study showed the importance of these two factors (Δ E, P ) in studying the conductance of the single molecular junction.