1,3-Propanediammonium and 1,12-dodecanediammonium encapsulated in the cavity of symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6]uril

The formation of host–guest inclusion complexes between symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6]uril (TMeQ[6]) and two alkyldiammonium guests (1,3-propanediammonium and 1,12-dodecanediammonium) in aqueous solution and in solid state has been confirmed by 1H NMR spectroscopy, X-ray crystallography and isothermal titration calorimetry (ITC). Their single-crystal X-ray diffraction analyses display that both guests take an extended conformation when bound within the TMeQ[6] cavity. ITC data reveal that the complexation of the alkyldiammonium guests with TMeQ[6] should take into account not only the ion–dipole interactions but also hydrophobic interactions. Moreover, we found that the stability constants for the complex formation of the +NH3(CH2)n with TMeQ[6] are much larger than with Q[6] because of the electron-denoting effects of the methyl groups.