This review describes the kinetics at play in Cucurbituril (CB[n])/guest recognition within a very wide time frame, from picoseconds to days. We cover the kinetics of (1) radiative and non‐radiative decays of fluorophores inside and outside CB[n]s, (2) guest motions in the CB[n] cavity, and (3) ingression, egression and threading mechanisms into, out of and through the macrocycles. We then show that the kinetics of guest release or capture can be controlled using CB[n]‐capped mesoporous systems and micelles, or by coupling those processes to the kinetics of ancillary reactions. The last section is devoted to the latest examples of reactions catalyzed and inhibited by CB[n]s.
The self-assembly into dynamic oligomers of Cucurbit[8]uril (CB[8]), a positive ditopic Ir(III) bis-terpyridine complex, and a negative ditopic Fe(II) bis-terpyridine complex flanked by four butyrate side chains was assessed to answer a seemingly straightforward question: does CB[8] adopt a social self-sorting pattern by encapsulating both positive and negative units into a heteroternary complex? We showed that this is indeed the case, with CB[8] linking a positive Ir unit to a neighboring negative Fe unit whenever possible. Furthermore, the solubility of the dynamic oligomers was significantly affected by their sequence; upon addition of 0.6-1.2 equiv of positive Ir oligomer to its negative Fe counterpart, the predominant assembly present in solution was a mixed oligomer with a (Fe-Ir-Ir-) sequence. Weak interactions between the negative butyrate side chains and the partially positive outer wall of CB[7] were also identified by two-dimensional nuclear magnetic resonance techniques, and resulted in a negative p K shift (0.10 p K unit) for the terminal carboxylic groups.
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