Heteromeric XB capsules have been reported from the selfassembly of suitably functionalised cavitands (Fig. ). Aakeröy and co-workers observed such a structure in the solid-state from interactions between calixarene macrocycle with four iodotetrafluorobenzene arms and a tetrapyridyl resorcinarene. Subsequently, Diederich and co-workers demonstrated the persistence of related architectures (81.82) in solution by NMR and were able to determine an association constant between the two components. Critically, small quantities of an alcohol were required to stabilise the structures through hydrogen-bonding interactions between the arms of the resorcinarene-based cavitands. The ability of these XB capsules to bind small guest molecules both in the solid state and in solution was also demonstrated. As an alternative design strategy, homomeric systems have also been reported in which XB donor-functionalised cavitands are assembled through interactions with iodonium ions (I + ), generally prepared via a pre-organised Ag(I) metallo-capsule intermediate (Fig. ). In this way, the halonium ions act as analogues of metal ions in coordination cage structures. Using this approach, Rissanen and co-workers have reported dimeric I3L2 166 and I4L2 assemblies, 167 I6L4 tetrahedra, 168 and a 4 nm I12L6 octahedron. As with MOCs, subtle changes to the ligand structure can have a significant impact on the resultant assembly: whilst ligand 83 with imidazole donor units yielded an I3L2 prismatic cage, DABCO ligand 84 formed an I6L4 tetrahedron. Aside from characterisation by SCXRD in the solid-state and by MS, the persistence of these species in solution has been demonstrated by NMR and DOSY. Typically, these experiments have been run in low polarity solvents such as dichloromethane or chloroform, although stability in acetonitrile has also been demonstrated. Dimeric capsules assembled through chalcogen-bonding interactions have also been reported (Fig. ). By incorporating benzotelluradiazole and benzothiadiazole moieties into resorcinarene cavitands, Diederich and co-workers showed that these were capable of self-assembly into [1+1] capsules in solution and the solid-state. Crucially, for the capsule dimers to form, the cavitands were required to adopt a vase conformation. The significantly stronger ChB interactions with tellurium resulted in persistence of 85 Te 2 across a range of solvents (dichloromethane, benzene and THF) and concentrations (down to 40 μM in THF). In contrast, 85 S 2 only formed in benzene and THF, resulting from complementary binding of solvent molecules within the cavitand cavity favouring the vase form, whilst in dichloromethane 85 S adopted a kite conformation, preventing capsule formation. Rebek, Yu and co-workers investigated related benzoselenadiazole systems with water-solubilising substituents attached to the lower rim. Although by itself cavitand 85 Se adopted a kite conformation in D2O, addition of suitable guests induced formation of [1+1] capsules templated through incorporating one (e.g. n-nonane) or two (e.g. n-pentane, cyclohexane) guest molecules. HB, XB and ChB capsules can be studied in solution by NMR techniques, including DOSY. Of special note, self-assembly of the XB capsules reported by Diederich and co-workers (81.82), that incorporated perfluorinated iodophenyl XB donors, could be followed by F NMR, and close spatial proximity of the acceptor and donor cavitands evidenced by 1 H, F HOESY experiments. MS is also commonly employed, as is SCXRD in the solid-state, although the relatively weak nature of some HB/XB/ChB interactions can make successful crystallisation of these capsules difficult.