Previous studies on selective encapsulation between host and guest molecules concluded that size matching is a critical factor in host-guest binding. It is inferred by comparing the size of various molecules that the C 18 with diameter of 7.4 Å is expected to match the cavities of OPP (the long and short axis lengths are about 19.3 and 14.5 Å, respectively), enabling the combination of them into a host-guest supramolecular complex (Scheme 1).