Photophysical Activity and Host-Guest Behavior of Ruthenium Polypyridyl Catalysts Encapsulated in Cucurbit[10]uril

This work outlines a strategy to combine the use of visible light and confined spaces to form a supramolecular photocatalyst system. Polypyridyl ruthenium(II) complexes [Ru(bpy)₃]²⁺ (bpy = 2,2'-bipyridine), [Ru(bpy)₂(bpm)]²⁺ (bpm = 2,2'-bipyrimidine), and [Ru(bpy)₂(bpz)]²⁺ (bpz = 2,2'-bipyrazine) are encapsulated in cucurbit[10]uril to form host-guest systems in aqueous solution. The photophysical properties of the complexes are altered by encapsulation, with improved emissive behavior for the heteroleptic complexes. Oxidative quenching of the photocatalyst's excited state via intermolecular charge transfer to methyl viologen can occur within the internal cavity, which acts to preorganize the reagents. The host-guest system containing [Ru(bpy)₃]²⁺ can bind suitable substrates, and essential criteria for its use as a supramolecular photocatalyst are investigated.