Preparation, Characterization, Redox Properties, and UV−Vis−NIR Spectra of Binuclear Ruthenium Complexes [{(Phtpy)(PPh3)2Ru}2{C⋮C−(CHCH)m−C⋮C}]n+ (Phtpy = 4‘-phenyl-2,2‘:6‘,2‘ ‘-terpyridine)

Abstract

A series of C4−C10 bridged Ru2II,II complexes [{(Phtpy)(PPh3)2Ru}2(C⋮C−(CHCH)m−C⋮C)]2+ (m = 0, 1, 2, 3) were prepared by reaction of [(Phtpy)(PPh3)2Ru(acetone)]2+ with Me3Si−C⋮C−(CHCH)m−C⋮C−SiMe3 in the presence of potassium fluoride. Oxidation of the Ru2II,II complexes by 1 equiv of ferrocenium hexafluorophosphate gave the stable Ru2II,III mixed-valence complexes [{(Phtpy)(PPh3)2Ru}2(C⋮C−(CHCH)m−C⋮C)]3+ when m = 0, 1, or 2. These complexes were all characterized by microanalyses, ESI-MS, 1H and 31P NMR, IR, and UV−vis−NIR spectroscopy, cyclic and differential pulse voltammetry, and X-ray crystallography for compound [1](PF6)2. The wave separations ΔE1/2 (E1/2A − E1/2B) due to stepwise oxidation of two RuII into RuIII are 0.610, 0.260, 0.165, and <0.070 V for m = 0−3, respectively, in dichloromethane solutions, revealing a significant dependence of the electronic communication on metal−metal distances. The visible−NIR spectral studies on the Ru2II,III mixed-valence complexes [{(Phtpy)(PPh3)2Ru}2(C⋮C−(CHCH)m−C⋮C)]3+ (m = 0, 1, 2) demonstrated that electronic delocalization along the molecular rods attenuates dramatically with the increase of the ethenyl number.