Energetics and Electronic Structures of Inclusion Compounds of Large Fullerenes and Cycloparaphenylenes

The energetics and electronic structures of large fullerenes included within [n]cycloparaphenylenes ([n]CPPs) are investigated using density functional theory. We observe that the large fullerenes included within [n]CPP ([n]CPP ⊃ Cn, where n = 76 and 78) are energetically stable and the inclusion reactions are exothermic for the [n]CPP with a diameter of 1.49 nm or larger. Owing to the electronic states of the guest fullerene molecules and the host [n]CPP, [n]CPP ⊃ C60 possesses a staggered electronic structure near the energy gap between the highest occupied and lowest unoccupied states, leading to a narrower energy gap than that of fullerenes and CPP. We also demonstrate that the electron states associated with the fullerene exhibit an upward shift upon inclusion owing to the quantum confinement effect on the π states of fullerenes by the CPP.