The configurational superpositions of the respective free and composite states of C 18 and OPP indicate that their structural changes caused by intermolecular interactions are very slight (Figure ). Natural population analyses (NPAs) reveal that the charge transfers between the C 18 and the loop accommodating it in complexes are all only a negligible 0.03 e, and the charges of two sides of the complexes are almost isolated from each other (Table ). These results indicate that the geometric and electronic structures of host-guest encapsulations on both sides of complexes are independent.