Simultaneous Bridge-Localized and Mixed-Valence Character in Diruthenium Radical Cations Featuring Diethynylaromatic Bridging Ligands

• Published in: Journal of the American Chemical Society 2011-11, Vol.133 (45), p.18433-18446
• Main Authors: Fox, Mark A, Le Guennic, Boris, Roberts, Rachel L, Brue, Daniel A, Yufit, Dmitry S, Howard, Judith A. K, Manca, Gabriele, Halet, Jean-François, Hartl, František, Low, Paul J
• Format: Article
• Language: English
• Subjects: Cations - chemistry; Chemical Sciences; Free Radicals - chemistry; Hydrocarbons, Aromatic - chemistry; Inorganic chemistry; Ligands; Models, Molecular; Molecular Structure; or physical chemistry; Organometallic Compounds - chemistry; Quantum Theory; Ruthenium - chemistry; Theoretical and
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja207827m

A series of bimetallic ruthenium complexes [{Ru(dppe)Cp*}2(μ-CCArCC)] featuring diethynylaromatic bridging ligands (Ar = 1,4-phenylene, 1,4-naphthylene, 9,10-anthrylene) have been prepared and some representative molecular structures determined. A combination of UV–vis–NIR and IR spectroelectrochemical methods and density functional theory (DFT) have been used to demonstrate that one-electron oxidation of compounds [{Ru(dppe)Cp*}2(μ-CCArCC)](HCCArCCH = 1,4-diethynylbenzene; 1,4-diethynyl-2,5-dimethoxybenzene; 1,4-diethynylnaphthalene; 9,10-diethynylanthracene) yields solutions containing radical cations that exhibit characteristics of both oxidation of the diethynylaromatic portion of the bridge, and a mixed-valence state. The simultaneous population of bridge-oxidized and mixed-valence states is likely related to a number of factors, including orientation of the plane of the aromatic portion of the bridging ligand with respect to the metal d-orbitals of appropriate π-symmetry.