Ruben Mario, Landa Aitor, Lörtscher Emanuel, Riel Heike, Mayor Marcel, Görls Helmar, Weber Heiko B, Arnold Andreas, Evers Ferdinand
Institute of Nanotechnology, Karlsruhe Institute of Technology, PF 3640, 76021 Karlsruhe, Germany.
Small. 2008 Dec;4(12):2229-35. doi: 10.1002/smll.200800390.
The charge transport through a single ruthenium atom clamped by two terpyridine hinges is investigated, both experimentally and theoretically. The metal-bis(terpyridyl) core is equipped with rigid, conjugated linkers of para-acetyl-mercapto phenylacetylene to establish electrical contact in a two-terminal configuration using Au electrodes. The structure of the Ru(II)(L)(2)(2) molecule is determined using single-crystal X-ray crystallography, which yields good agreement with calculations based on density functional theory (DFT). By means of the mechanically controllable break-junction technique, current-voltage (I-V), characteristics of Ru(II)(L)(2)(2) are acquired on a single-molecule level under ultra-high vacuum (UHV) conditions at various temperatures. These results are compared to ab initio transport calculations based on DFT. The simulations show that the cardan-joint structural element of the molecule controls the magnitude of the current. Moreover, the fluctuations in the cardan angle leave the positions of steps in the I-V curve largely invariant. As a consequence, the experimental I-V characteristics exhibit lowest-unoccupied-molecular-orbit-based conductance peaks at particular voltages, which are also found to be temperature independent.
