Interactions of α, ω-alkyldiammonium with inverted cucurbit[6]uril

Molecular interactions between an inverted cucurbit[6]uril (iQ[6]) with α,ω-alkyldiammonium guests (H3N(CH2)xNH3Cl2, x = 2, 4, 6, 8, 10, and 12 named 1–6) were investigated in aqueous and acidic solutions by various techniques. 1H NMR spectroscopy revealed that only compounds 3 and 4 underwent an equilibrium interaction with the iQ[6] host, with association constants in acidic solution of ~83 and ~41 L mol−1, respectively, while the other guests showed no obvious interaction. Only two host–guest interaction systems gave rise to single crystals in the presence of polychloride transition metal anions as structure-directing agents. X-ray diffraction revealed that guests 1 and 3 interacted with iQ[6] through portal and cavity interactions, respectively.