Synthesis, Structure, and Electronic Properties of a Dimer of Ru(bpy)2 Doubly Bridged by Methoxide and Pyrazolate

The heterobridged dinuclear complex cis,cis-[(bpy)2Ru(μ-OCH3)(μ-pyz)Ru(bpy)2]2+ (1; bpy = 2,2′-bipyridine; pyz = pyrazolate) was synthesized and isolated as a hexafluorophosphate salt. Its molecular structure was fully characterized by X-ray crystallography, 1H NMR spectroscopy, and ESI mass spectrometry. The compound 1·(PF6)2 (C44H38F12N10OP2Ru2) crystallizes in the monoclinic space group P21/c with a = 13.3312(4) A, b = 22.5379(6) A, c = 17.2818(4) A, β = 99.497(2)°, V = 5121.3(2) A3, and Z = 4. The meso diastereoisomeric form was exclusively found in the crystal structure, although the NMR spectra clearly demonstrated the presence of two stereoisomers in solution (rac and meso forms at approximately 1:1 ratio). The electronic properties of the complex in acetonitrile were investigated by cyclic voltammetry and UV−vis and NIR−IR spectroelectrochemistries. The stepwise oxidation of the RuII−RuII complex into the mixed-valent RuII−RuIII and fully oxidized RuIII−RuIII states is fully reversible on the time...