Mayer bond order essentially reflects the degree of electron delocalization or electron sharing between two atoms. The Mayer bond order of each pair of atoms between C 18 and OPP in 2C 18 @OPP was calculated and summed up to intermolecular value, and the result is merely 0.221. Such a small value indicates that the orbital interaction between the host and guest molecules is very weak, and hence the covalent and induction effects between them should be negligible.