Heterocalixarene inclusion chemistry. Structure of a crystalline host-guest complex including endo-calix ethyl acetate and exo-calix clustering of water

The X-ray crystal structure of the solvent inclusion compound formed betwee n heterocalix[8]arene 1, ethyl acetate and water (1 : 1 : 4.5) has been stu died. The compound crystallized in tetragonal space group I4(1)/a, a = b = 21.278(3), c = 31.290(4) Angstrom, V = 14167(4) Angstrom(3), Z = 8. The hos t molecule, incorporating benzimidazol-2-one and 2,5-dimethoxy-1,3-phenylen e subunits in an alternate cyclic arrangement, forms an almost perfectly cl osed cavity which encapsulates one solvent ethyl acetate guest molecule. Wa ter molecules being entrapped in the lattice cages in the form of cyclic an d linear clusters bind the bulky inclusion complexes via H-bonds in infinit e layers. Two symmetry center related benzimidazole-2-one moieties of two h osts from neighbouring layers in the crystal lattice are arranged such that they partially overlap exhibiting stacking interaction.