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

Here, we describe design, synthesis, and single-molecule conductance of ethynyl- and butadiynyl-ruthenium molecular wires with thioether anchor groups (RS= n -C 6 H 13 S, p - tert -Bu-C 6 H 4 S), trans -{RS-(C≡C) n } 2 Ru(dppe) 2 ( n = 1 ( 1 R ), 2 ( 2 R ); dppe: 1,2-bis(diphenylphosphino)ethane) and trans -( n -C 6 H 13 S-C≡C) 2 Ru{P(OMe) 3 } 4 3 hex . The organometallic molecular wires 1 R - 3 R are thermally stable under ambient conditions. 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-C 6 H 4 -(C≡C) n } 2 Ru(phosphine) 4 4 n (n= 1, 2) and trans -(Th-C≡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≡C) 2 } 2 Ru(dppe) 2 ( Au : gold metal electrode), shows conductance comparable to that of the covalently linked polyynyl wire with the similar molecular length, trans -{ Au -(C≡C) 3 } 2 Ru(dppe) 2 6 3 . DFT-NEGF study supports the highly conducting nature of the thioacetylene molecular wires through HOMO orbitals.