Structural, electronic and acid/base properties of [Ru(bpy(OH) 2) 3] 2+ (bpy(OH) 2 = 4,4′-dihydroxy-2,2′-bipyridine)

Michelle J. Fuentes, Richard J. Bognanno, William G. Dougherty, Walter J. Boyko, W. Scott Kassel, Timothy J Dudley, Jared J. Paul

Research output: Contribution to journalArticlepeer-review

27 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)12514-12523
Number of pages10
JournalDalton Transactions
Volume41
Issue number40
DOIs
StatePublished - Oct 28 2012
Externally publishedYes

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