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.

Modelling the luminescence of iridium cyclometalated complexes encapsulated in cucurbituril

Iridium(iii) cyclometalated complexes in aqueous solution often display relatively weak luminescence. It has been shown in previous work that this emission can be significantly enhanced (by up to two orders of magnitude) by encapsulation in cucurbit[10]uril (Q[10]). Luminescence lifetime measurements suggest a dynamic self-quenching mechanism is active, possibly due to displacement of an excited guest complex via collision with an unbound complex. We devise a model for the association of a group of iridium(iii) cyclometalated complexes with Q[10]. The model parameters are then fitted to steady-state emission titration curves. The excellent agreement of experimental data with the model provides valuable mechanistic information relating to the way this class of metal complexes interact and associate with the Q[10] host.

Ferrocene and ferrocenium inclusion compounds with cucurbiturils: a study of metal atom dynamics probed by Mössbauer spectroscopy

This study shows that Mössbauer spectroscopy is a sensitive probe of host–guest interactions and molecular motion in cucurbituril–ferrocene/ferrocenium complexes.

Solid-state study of the structure and host–guest chemistry of cucurbituril-ferrocene inclusion complexes

Solid-state host–guest interactions have been investigated for cucurbit[n]uril-ferrocene inclusion compounds (n = 7, 8) prepared via a microwave-assisted hydrothermal approach.