Vibrational excitations in single trimetal-molecule transistors

Single-molecule transistors incorporating trimetal molecules of Cu-3(dpa)(4)Cl-2 and Ni-3(dpa)(4)Cl-2 (dpa = 2,2'-dipyridylamide) have been fabricated. Conductance is measured as a function of bias and gate voltages at low temperature, showing single-electron tunneling behavior through the molecules. Additional structures corresponding to the excitations in the molecules are observed, which can be attributed to intramolecular vibrational excitations coupled to the electron tunneling processes. The energies of the vibrational states are dependent on the redox state of the included molecules.