title: Structural, electronic and acid/base properties of [Ru(bpy(OH)2)3]2+ (bpy(OH)2 = 4,4'-dihydroxy-2,2'-bipyridine).
abstract: We have synthesized the complex [Ru(bpy(OH)(2))(3)](2+) (bpy(OH)(2) = 4,4'-dihydroxy-2,2'-bipyridine) containing ligands that can be readily deprotonated. Both experimental and computational techniques were utilized to perform a thorough analysis of the structural and electronic properties of the complex in both the protonated and deprotonated state. The complex [Ru(bpy(OMe)(2))(3)](2+) (bpy(OMe)(2) = 4,4'-dimethoxy-2,2'-bipyridine) was also synthesized and studied, because the bpy(OMe)(2) ligand has electron-donating properties like bpy(OH)(2), but does not contain deprotonatable groups. Cyclic voltammetry of [Ru(bpy(OH)(2))(3)](2+) yields a reversible Ru(III/II) wave that shifts 1.43 V to lower energy upon deprotonation of the complex. UV/Visible absorbance spectroscopy reveals several Metal-to-Ligand Charge Transfer (MLCT) transitions that shift to lower energy upon deprotonation of the complex. This observation is in contrast to mixed-ligand systems containing deprotonatable groups, such as [Ru(bpy)(2)(bpy(OH)(2))](2+) (bpy = 2,2'-bipyridine) that demonstrate different types of electronic transitions assigned as mixed Metal-Ligand to Ligand Charge Transfer (MLLCT). The more symmetrical nature of the tris-bpy(OH)(2) complex most likely prevents the metal molecular orbitals from significantly mixing with the molecular orbitals of the deprotonated ligand. Luminescence studies were carried out on [Ru(bpy(OH)(2))(3)](2+) and reveal a shift to lower energy and quenching of the excited state upon deprotonation in accordance with the energy gap law.
authors.affiliation: Department of Chemistry, Villanova University, Villanova, Pennsylvania 19085, USA.
authors.forename: Michelle J
authors.initials: MJ
authors.lastname: Fuentes
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Bognanno
authors.forename: William G
authors.initials: WG
authors.lastname: Dougherty
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Boyko
authors.forename: W Scott
authors.initials: WS
authors.lastname: Kassel
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Dudley
authors.forename: Jared J
authors.initials: JJ
authors.lastname: Paul