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-C4k+2)[Ru2(ap)4] (compounds 4k+2b with k = 2, 3, and 4) were prepared from the Glaser coupling reaction between Ru2(Xap)4(C2k+2H) and Ru 2(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 [Ru 2-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.

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Journal American Chemical Society Journal
Cao, Z. (Zhi), Xi, B. (Bin), Jodoin, D.S. (Diane S.), Zhang, L. (Lei), Cummings, S.P. (Steven P.), Gao, Y. (Yang), … Ren, T. (Tong). (2014). Diruthenium-polyyn-diyl-diruthenium wires: Electronic coupling in the long distance regime. American Chemical Society Journal, 136(34), 12174–12183. doi:10.1021/ja507107t