Toward supramolecular polymers incorporating double cavity cucurbituril hosts

We describe the synthesis of a series of guests (1-6) containing two adamantylammonium ions separated by xylylene spacing groups and their complexation properties toward double cavity cucurbituril host bis-ns-CB[10]. We observed the preferential formation of 1:1, 2:2, and oligomeric complexes rather than the desired n:n supramolecular polymers. Guest 7, which contains a longer biphenyl spacer successfully precludes the formation of the 1:1 complex but results in the formation of the 2:2 complex (bis-ns-CB[10]2·72) rather than supramolecular polymer. Guest 8, which contains adamantylammonium, p-xylylene diammonium, and hexanediammonium ion binding regions is shown to reversibly form 2:2 and 1:2 complexes (bis-ns-CB[10]2·82 and bis-ns-CB[10]·82) in response to changes in host:guest stoichiometry. Lastly, this equilibrium can be manipulated by the addition of exogenous CB[6], which selectively targets the hexanediammonium ion binding region of 8 and delivers the penta-molecular complex bis-ns-CB[10]·82·CB[6]2.

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