Electrochemical gating of single osmium molecules tethered to Au surfaces

HERRERA S.; CALVO EJ,; ALEJANDRA M. RICCI; C. ADAM

JOURNAL OF SOLID STATE ELECTROCHEMISTRY (PRINT)

SPRINGER

Lugar: Berlin; Año: 2016 vol. 20 p. 957 - 967

1432-8488

The electrochemical study of electron transport between Au electrodes and the redox molecule Os[(bpy)2(PyCH2 NH2CO-]ClO4 tethered to molecular linkers of different length (1.3 to 2.9nm) to Au surfaces has shown an exponential decay of the rate constant kET0 with a slope β = 0.53 consistent with through bond tunneling to the redox center.Electrochemical gating of single osmium molecules in an asymmetric tunneling nano-gap between a Au(111) substrate electrode modified with the redox molecules and a Pt-Ir tip of a scanning tunneling microscope was achieved by independent control of the reference electrode potential in the electrolyte, Eref − Es, and the tipsubstrate bias potential, Ebias. Enhanced tunneling current at the osmium complex redox potential was observed as compared to the off resonance set point tunneling current with a linear dependence of the overpotential at maximum current vs.the Ebias.This corresponds to a sequential two-electron transfer with partial vibration relaxation from the substrate Au(111)to the redox molecule in the nano-gap and from this redox state to the Pt-Ir tip according to the model of Kuznetsov and Ulstrup(JPhysChem A 104: 11531, 2000). Comparison of short and long linkers of the osmium complex has shown the same two-step ET(electron transfer) behavior due to the long time scale in the complete reduction-oxidation cycle in the electrochemical tunneling