  Recent experimental realization [J. Am. Chem. Soc., 127 (2005) 7328] of
various dithiocarbamate self assembly on gold surface opens the possibility for
use of dithiocarbamate linkers to anchor molecular wires to gold electrodes.
  In this paper, we explore this hypothesis computationally. We computed the
electron transport properties of 4,4'-bipyridine (BP),
4,4'-bipyridinium-1,1'-bis(carbodithioate) (BPBC),
  4-(4'-pyridyl)-peridium-1-carbodithioate (BPC) molecule junctions based on
the density functional theory and non-equilibrium Green's functions. We
demonstrated that the stronger molecule-electrode coupling associated with the
conjugated dithiocarbamate linker broadens transmission resonances near the
Fermi energy. The broadening effect along with the extension of the $\pi$
conjugation from the molecule to the gold electrodes lead to enhanced
electrical conductance for BPBC molecule. The conductance enhancement factor is
as large as 25 at applied voltage bias 1.0 V.
  Rectification behavior is predicted for BPC molecular wire junction, which
has the asymmetric anchoring groups.
