Redox-Active Molecular Wires Incorporating Ruthenium(II) σ-Arylacetylide Complexes for Molecular Electronics

The preparation and properties of novel ruthenium carbon-rich complexes for molecular electronics are reported. The synthetic procedure used in this work led to the first series of neutral redox-active conjugated molecular wires including mono-, bi-, and trimetallic bis(σ-arylacetylide) complexes (Ru n NC and CNRu n NC, n = 1–3) having 1,4-diethynylbenzene spacers and one or two isocyanide terminal groups for surface binding. An analogous cationic σ-arylacetylide-allenylidene molecule (AllRuNC + ) is also reported. These new structurally rigid complexes have lengths ranging from 1.8 to 4.5 nm and are excellent candidates for the building of alternative metal−molecule−metal junctions. Indeed, the molecules uniquely contain up to three metal-redox centers that are efficiently coupled by conjugated ligands to provide significant electronic communication along the molecular backbone, as indicated by the optical and electrochemical properties. Furthermore, the wires offer multiple low potential redox states that can lead to unusual current–voltage behavior and efficient charge conduction. Overall, these molecules will open a route to establish the structure–property relationships of conductive molecular wires and to gain valuable insights into the correlation between charge transport and molecular length.