Fullerene size controls the selective complexation of [11]CPP with pristine and endohedral fullerenes

Abstract

The ability of the carbon nanoring [11]cycloparaphenylene ([11]CPP) for coordinating fullerenes has been tested using a series of hosts, including the pristine fullerenes C₆₀, C₇₀, C₇₆ and C₇₈, the clusterfullerene Sc₃N@C₈₀, monometallic endofullerenes Y@C₈₂ and Tm@C₈₂, and dimetallic endofullerenes Y₂@C₈₂ and Lu₂@C₈₂. A systematic theoretical study employing dispersion corrected density functional methods has been carried out in order to explore the characteristics of the complexes and the strength of the interaction. Depending on the dimer, complexation energies span from around −36 kcal mol⁻¹ with C₆₀ to −53 kcal mol⁻¹ with the C₈₂ derivatives. Dispersion is the main stabilizing contribution in these dimers, so the molecules arrange to maximize the number of close interatomic contacts. Since most fullerenes can properly fill the cavity of the nanoring the stability of the complexes is pretty similar, with the exception of the smallest fullerenes. The complexes with endohedral fullerenes show similar stabilities in all cases studied, with no noticeable dependence on the nature of the endohedral species. The results obtained suggest that fullerenes larger than C₇₆ could be selectively encapsulated by [11]CPP compared to smaller fullerenes.