Carcerands are ‘closed-surface, globe-shaped compounds with enforced hollow interiors’ (ref. 1) that imprison template molecules during shell closure. Hemicarcerands possess holes in their shells which, while they do not prevent the isolation and characterization of complexes (‘hemicarceplexes’), do allow entry and departure of guests (ref. 2). Space-filling models have guided the design of these molecules, and a number of the designs have been confirmed by X-ray crystal structure analysis. However, the nature of the host-guest interaction is seldom established by the crystal structure, presumably because of thermal or static disorder of the guest and/or external solvent molecules. While the presence of the guest, and its motional state, can be determined by other methods, the size and shape of the cavity and its relationship to the guest may be more completely described by the molecular models or the related, more quantitative, atom-atom potentials (ref. 3). Potential-energy studies require atomic positions from crystal structures or from molecular mechanics. In this paper we explore the cavities of three hemicarceplexes, and compare and contrast their host-guest interactions with those in ‘velcraplexes’ (ref. 4). ‘Velcrands’ do not encapsulate guests but instead form four-fold, lock-key dimers (‘velcraplexes’), with large surfaces of contact between monomers. In the present dimers, the keys and locks are, respectively, methyl groups and corresponding holes that serve to position and hold the monomers in place. Both homo- and hetero-dimers may be formed, with a wide range of intra-complex non-bonded contacts and corresponding free energies of binding. © 1993 IUPAC
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Choi, H. J., Cram, D. J., Knobler, C. B., & Maverick, E. F. (1993). Characterization of cavities in carcerands. Pure and Applied Chemistry, 65(3), 539–543. https://doi.org/10.1351/pac199365030539