Crystal and Molecular Structure of Double Macrocyclic Inclusion Complexes, γ-Cyclodextrin·12-Crown-4·NaCl, a Model for the Transport of Ions through Membranes

The crystal structure of a γ-cyclodextrin·12-crown-4·NaCl (3 : 3 : 1) inclusion complex was determined by an X-ray method to be space group P4212, a=b=23.816(3) Å, c=23.072(3) Å. The inclusion complex has a C4 symmetry, and the cation, Na+, is coordinated by two 12-crown-4 molecules in a hydrophobic channel formed by tail-to-tail oriented two γ-cyclodextrin molecules.