  Tunneling spectroscopy measurements have been carried out on a single
molecule device formed by two Pd nanocrystals (dia, $\sim$5 nm) electronically
coupled by a conducting molecule, dimercaptodiphenylacetylene. The I-V data,
obtained by positioning the tip over a nanocrystal electrode, exhibit negative
differential resistance (NDR) on a background M-I-M characteristics. The NDR
feature occurs at $\sim$0.67 V at 300 K and shifts to a higher bias of 1.93 V
at 90 K. When the tip is held in the middle region of the device, a coulomb
blockade region is observed ($\pm\sim$0.3 V).
