E and Z Secondary Amides in Supramolecular Nanotubes and Nanospheres - Molecular Self-Assembly: Advances and Applications - page 50

2.5 Supramolecular Spheres

Bowl-shapedmoleculeslikeglycoluryl[70,71],cyclotriveratrylenes
(CTV) [34], calixarenes, and their derivatives [72-78] have often
beenusedtosculpturevarioushostguestcomplexes(Fig.2.14).
Such architectures can be either reversible like cavitands, capsules,
andhemicarcerandsorirreversiblelikecarcerands.Capsulesofer
thepossibilitytocraftdynamicglobularcavitiesthatcanfind
applicationsintransportandcatalysis(Fig.2.15).

Figure 2.14 (a) Curved motifs and backbones often used as hosts in

host-guest complexes. (b) An empty dimeric glycoluryl
capsule. (c) A dimeric substituted resorcinarene capsule
with a tetramethylammonium cation as a guest.

Some man-made molecular capsules can mimic viral protein
capsids [79]. However, all fully synthetic objects remain incredibly
small in terms of sheer size and number of units by comparison
with average natural architectures. Indeed, many natural globular
proteinsaresymmetricoligomersconsistingofasmanyas60units