Molecular Conductances of Styryl Ruthenium and Divinylphenylene-Bridged Diruthenium Complexes with Thioanisyl Anchor Groups

We report the synthesis of new mononuclear styryl and dinuclear divinylphenylene-bridged diruthenium complexes, terminated on both ends with thiomethyl (−SMe) substituents at the styryl and the bidentately coordinating benzoate or β-acetylphenolate chelate ligands. Robust binding of the SMe functionalities to surface atoms of nanoscale gold electrodes enables the modified complex molecules to establish nanojunctions in scanning tunneling microscopy break-junction experiments. Ten of the 13 complexes provided defined molecular conductance features that could be evaluated. Complexes with β-ketoenolate ligands proved to be somewhat better conductors than those with benzoate ligands, and the dinuclear complexes, despite their considerably larger molecular lengths, proved to be more conductive than the mononuclear ones. While the molecular conductances of the present complexes are at the low end of those with rigid-rod fully π-conjugated ethynylarylene backbones and linkages, their modular design makes this type of complex a versatile testbeds for probing the impact of every constituent on the molecular conductances of such metal complex-based wires.