Guest packing motifs within a supramolecular nanocapsule and a covalent analogue

Two hosts that utilize the hydrophobic effect to assemble and/or encapsulate guest molecules were studied. The hosts, octa-acid (OA) and hexalene diamine-linked octa-acid (HOA), were shown to complex a broad range of n-alkanes up to n-hexacosane (C26H54). A combination of (1)H NMR, NMR diffusion, COSY, and NOESY experiments revealed four different guest packing motifs, depending on the size of the guest and the nature of the host. As a function of guest size, smooth transitions from one motif to the next were observed and allowed qualification of their relative stabilities. Furthermore, although the two hosts engender ostensibly identical encapsulation environments, their different assembly properties lead to quite distinct packing-motif profiles, i.e., how the motifs change as a function of guest size.