The IR spectroscopy of OPP, C 18 @OPP, and 2C 18 @OPP presented are similar in most of the regions (Figure ), but there are three significant differences: (1) The introduction of C 18 does not affect the wavenumber of the very strong IR absorption at about 800.0 cm -1 , but there is a conspicuous enhancement of the absorption intensity with the addition of C 18 . (2) The addition of C 18 introduces a remarkable IR absorption at about 400.0 cm -1 , and the more C 18 is complexed the stronger the spectroscopic intensity at this wavenumber. We found this absorption comes entirely C 18 @OPP, and 2C 18 @OPP. The Lorentz and Gaussian functions with half-width at half height of 5.0 and 3000.0 cm -1 were employed for broadening the theoretical data as IR spectroscopy and UV-Vis absorption spectrum, respectively. A fundamental scale factor of 0.949 was applied for all vibrational frequencies. The dash-dot and short-dash curves represent charge-transfer spectra (CTSs) caused by electronic excitation within OPP and that from OPP to C 18 , respectively, and other forms of electronic excitation, that is, those from C 18 to OPP and within C 18 , are almost undetectable.