Ligands with multiple protonation states provide an opportunity to significantly alter the electronic properties of metal complexes. Understanding how to manipulate these electronic properties can influence the development of catalysts and catalytic control. For example, increasing electronic density around the metal center through deprotonation of the ligand could activate a catalyst that is inactive in the protonated state, resulting in a controllable on/off switch for catalysis. As a result, we are interested in the development of pH-dependent ligands and understanding how positioning of acid/base dependent functional groups within the ligand impact metal complexes structural and electronic properties. Three ruthenium complexes have been synthesized containing asymmetric bipyridine ligands. Specifically, [Ru(bpy)2(4bpy(OH))]2+ (bpy = 2,2'-bipyridine; 4bpy(OH) = 4-hydroxy-2,2'-bipyridine), [Ru(bpy)2(4bpy(OMe))]2+ (4bpy(OMe) = 4-methoxy-2,2'-bipyridine), and [Ru(bpy)2(4,4'bpy(OH)(OMe))]2+ (4,4'bpy(OH)(OMe) = 4-hydroxy-4'-methoxy-2,2'-bipyridine) were synthesized as both hexafluorophosphate and chloride salts. Characterization was carried out using infrared, NMR, and UV-Visible spectroscopies. In addition, cyclic voltammetry and pH-dependent UV-Visible spectroscopy was utilized to study the metal complexes electronic properties as a function of pH environment.

Electronic properties of ruthenium complexes containing asymmetric pH-dependent polypyridyl ligands

2019 Spring National Meeting

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