Host-guest inclusion complexes formed between a symmetrical tetrasubstituted cucurbit[6]uril and glycine

Herein, we have investigated the host-guest inclusion complexes formed on interaction of the symmetric tetramethyl-substituted cucurbit[6]uril (TMeQ[6]) with glycine (Gly) under different conditions. The interactions have been studied both in solution (by H-1 NMR spectroscopy and mass spectrometry) and in the solid state by single crystal X-ray diffraction. The molecular structures of two products are reported, namely TMeQ[6]center dot(H2O)(2)(PO4)(NH3CH2COOH)(2) (1) and TMeQ[6]center dot Ca(H2O)(5)center dot(Cl)(3)(NH3CH2COOH)center dot 16H(2)O (2). Complex 1 adopts a hydrogen-bonded dimeric structure with two glycinium ions contained within a TMeQ[6] molecule with the NH3+ portions of the two molecules located just above the opposite rims of the bowl and forming hydrogen bonds with C-O. In 2, there are centrosymmetric dimers bridged by pairs of calcium ions.