title: Diruthenium-polyyn-diyl-diruthenium wires: electronic coupling in the long distance regime.
abstract: Reported herein is a series of Ru2(Xap)4 capped polyyn-diyl compounds, where Xap is either 2-anilinopyridinate (ap) or its aniline substituted derivatives. Symmetric [Ru2(Xap)4](μ-C4k)[Ru2(Xap)4] (compounds 4ka (X = 3-isobutoxy) and 4kc (X = 3,5-dimethoxy) with k = 2, 3, 4, and 5) was obtained from the Glaser coupling reaction of Ru2(Xap)4(C2kH). Unsymmetric [Ru2(Xap)4](μ-C(4k+2))[Ru2(ap)4] (compounds 4k+2b with k = 2, 3, and 4) were prepared from the Glaser coupling reaction between Ru2(Xap)4(C(2k+2)H) and Ru2(ap)4(C2kH). X-ray diffraction study of compound 12c revealed both the sigmoidal topology of the polyyn-diyl bridge and the fine structural detail about the Ru2 cores. Cyclic and differential pulse voltammetric (CV and DPV) measurements and spectroelectrochemical studies revealed that (i) the reduced monoanions [Ru2-C2m-Ru2](-1) (m = 4-8) belong to the Robin-Day class II mixed valent ions and (ii) the electronic coupling between Ru2 termini depends on the length of the polyyn-diyl bridge with an attenuation constant (γ) between 0.12 and 0.15 Å(-1). In addition, spin-unrestricted DFT calculations provide insight about the nature of orbitals that mediate the long distance electronic coupling.
authors.affiliation: Department of Chemistry, Purdue University , West Lafayette, Indiana 47907, United States.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Cao
authors.forename: Bin
authors.initials: B
authors.lastname: Xi
authors.forename: Diane S
authors.initials: DS
authors.lastname: Jodoin
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Steven P
authors.initials: SP
authors.lastname: Cummings
authors.forename: Yang
authors.initials: Y
authors.lastname: Gao
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Tyler
authors.forename: Phillip E
authors.initials: PE
authors.lastname: Fanwick
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Crutchley
authors.forename: Tong
authors.initials: T
authors.lastname: Ren