Synthesis, Electrochemistry, and Single-Molecule Conductance of Bimetallic 2,3,5,6-Tetra(pyridine-2-yl)pyrazine-Based Complexes

Ross Davidson; Jing-Hong Liang; David Costa Milan; Bing-Wei Mao; Richard J Nichols; Simon J Higgins; Dmitry S Yufit; Andrew Beeby; Paul J Low

doi:10.1021/acs.inorgchem.5b00507

Synthesis, Electrochemistry, and Single-Molecule Conductance of Bimetallic 2,3,5,6-Tetra(pyridine-2-yl)pyrazine-Based Complexes

Inorg Chem. 2015 Jun 1;54(11):5487-94. doi: 10.1021/acs.inorgchem.5b00507. Epub 2015 May 14.

Authors

Ross Davidson¹, Jing-Hong Liang^{2

3}, David Costa Milan², Bing-Wei Mao³, Richard J Nichols², Simon J Higgins², Dmitry S Yufit¹, Andrew Beeby¹, Paul J Low⁴

Affiliations

¹ †Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K.
² ‡Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
³ §State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China.
⁴ ∥School of Chemistry and Biochemistry, University of Western Australia, 35 Stirling Highway, Perth, Western Australia 6009, Australia.

PMID: 25974862
DOI: 10.1021/acs.inorgchem.5b00507

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.