Templating Effects in the Dynamic Chemistry of Cucurbiturils and Hemicucurbiturils

This review concentrates on the remarkable macrocyclisation chemistry of cucurbituril family members. During a single step in the condensation reaction of cucurbit[6]uril or hemicucurbit[12]uril 24 new C−N bonds are formed. In the case of hemicucurbit[12]uril this leads to the highly efficient formation of a covalently bound chain of 48 atoms. This phenomenon is possible because all cucurbiturils are built up of dynamic covalent acylaminal linkers. Moreover, the reversibility of acylaminal linkages makes the formation of macrocycles susceptible to external stimuli. Influence of the chain-growth and chain-cycle equilibrium and the effect of different templates in CB chemistry is discussed. As anions have a pronounced effect on formation of hemicucurbiturils, a comprehensive overview on their role in modifying the solid-state structures of hemicucurbiturils is given.