title: Synthesis, Electrochemistry, and Single-Molecule Conductance of Bimetallic 2,3,5,6-Tetra(pyridine-2-yl)pyrazine-Based Complexes.
abstract: The ligands 4'-(4-(methylthio)phenyl)-2,2':6',2″-terpyridine (L(1)), 4'-((4-(methylthio)phenyl)ethynyl)- 2,2':6',2″-terpyridine (L(2)), and bis(tridentate) bridging ligand 2,3,5,6-tetra(pyridine-2-yl)pyrazine (tpp) were used to prepare the complexes [Ru(L(1))2][PF6]2 ([1][PF6]2, [Ru(L(2))2][PF6]2 ([2][PF6]2), [{(L(1))Ru}(μ-tpp){Ru(L(1))}][PF6]4 ([3][PF6]4), and [{(L(2))Ru}(μ-tpp){Ru(L(2))}][PF6]4 ([4][PF6]4). Crystallographically determined structures give S···S distances of up to 32.0 Å in [4](4+). On the basis of electrochemical estimates, the highest occupied molecular orbitals of these complexes fall between -5.55 and -5.85 eV, close to the work function of clean gold (5.1-5.3 eV). The decay of conductance with molecular length across this series of molecules is approximately exponential, giving rise to a decay constant (pseudo β-value) of 1.5 nm(-1), falling between decay factors for oligoynes and oligophenylenes. The results are consistent with a tunnelling mechanism for the single-molecule conductance behavior.
authors.affiliation: †Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K.
authors.forename: Ross
authors.initials: R
authors.lastname: Davidson
authors.affiliation: ‡Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.|§State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China.
authors.forename: Jing-Hong
authors.initials: JH
authors.lastname: Liang
authors.affiliation: ‡Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
authors.forename: David
authors.initials: D
authors.lastname: Costa Milan
authors.affiliation: §State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China.
authors.forename: Bing-Wei
authors.initials: BW
authors.lastname: Mao
authors.affiliation: ‡Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Nichols
authors.affiliation: ‡Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Higgins
authors.affiliation: †Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K.
authors.forename: Dmitry S
authors.initials: DS
authors.lastname: Yufit
authors.affiliation: †Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K.
authors.forename: Andrew
authors.initials: A
authors.lastname: Beeby
authors.affiliation: ∥School of Chemistry and Biochemistry, University of Western Australia, 35 Stirling Highway, Perth, Western Australia 6009, Australia.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Low