Inorganic Chemistry, Vol.51, No.7, 4390-4397, 2012
9-Oxidophenalenone: A Noninnocent beta-Diketonate Ligand?
The redox systems [Ru(L)(bpy)(2)](k), [Ru(L)(2)(bpy)](m), and [Ru(L)(3)](n) containing the potentially redox-active ligand 9-oxidophenalenone = L- were investigated by spectroelectrochemistry (UV-vis-near-IR and electron paramagnetic resonance) in conjunction with density functional theory (DFT) calculations. Compounds [Ru(L-)(bpy)(2)]ClO4 ([1]ClO4) and [Ru(L-)(2)(bpy)]ClO4 ([2]ClO4) were structurally characterized. In addition to establishing electron-transfer processes involving the Ru-II/Ru-III/Ru-IV. and bpy(0)/bpy(center dot-) couples, evidence for the noninnocent behavior of L- was obtained from [Ru-IV(L-center dot)(L-)(bpy)](3+), which exhibits strong near-IR absorption due to ligand-to-ligand charge transfer. In contrast, the lability of the electrogenerated anion [Ru(L)(2)(bpy)](-) attributed to a resonance situation [Ru-II(L center dot 2-)(L-)(bpy)](-)/[Ru-II(L-)(2) (bpy(center dot-))](-), as suggested by DFT calculations.