Charge Transport Through a Cardan-Joint Molecule

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)](PF6)(2) molecule is determined using single-crystal X-ray crystallography, which yields good agreement with calculations based on density functional theory (LIFT). By means of the mechanically controllable break-junction technique, current voltage (I-V), characteristics of [RUII(L)(2)](PF6)(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.