Organometallic Molecular Wires with Thioacetylene Backbones, trans-{RS-(C≡C)n}2Ru(phosphine)4: High Conductance through Non-Aromatic Bridging Linkers

In this work, the design, synthesis, and single-molecule conductance of ethynyl- and butadiynyl-ruthenium molecular wires with thioether anchor groups [RS=n-C6H13S, p-tert-Bu-C6H4S), trans-{RS-(C equivalent to C)(n)}(2)Ru(dppe)(2) (n=1 (1 (R)), 2 (2 (R)); dppe: 1,2-bis(diphenylphosphino)ethane) and trans-(n-C6H13S-C equivalent to C)(2)Ru{P(OMe)(3)}(4) 3(hex)] are reported. Scanning tunneling microscope break-junction study has revealed conductance of the organometallic molecular wires with the thioacetylene backbones higher than that of the related organometallic wires having arylethynylruthenium linkages with the sulfur anchor groups, trans-{p-MeS-C6H4-(C equivalent to C)(n)}(2)Ru(phosphine)(4) 4(n) (n=1, 2) and trans-(Th-C equivalent to C)(2)Ru(phosphine)(4) 5 (Th=3-thienyl). It should be noted that the molecular junctions constructed from the butadiynyl wire 2 (R), trans-{Au-RS-(C equivalent to C)(2)}(2)Ru(dppe)(2) (Au: gold metal electrode), show conductance comparable to that of the covalently linked polyynyl wire with the similar molecular length, trans-{Au-(C equivalent to C)(3)}(2)Ru(dppe)(2) 6(3). The DFT non-equilibrium Green's function (NEGF) study supports the highly conducting nature of the thioacetylene molecular wires through HOMO orbitals.

Automated summary

This work presents the design, synthesis, and single-molecule conductance of ethynyl- and butadiynyl-ruthenium molecular wires with thioether anchor groups. The study shows that the conductance of thioacetylene backbones is higher than that of arylethynylruthenium linkages with sulfur anchor groups. Moreover, the butadiynyl wire displays conductance comparable to covalently linked polyynyl wire of similar length. DFT study supports the highly conducting nature of thioacetylene molecular wires through HOMO orbitals.