A molecular Popeye: Li@C and its complexes with []cycloparaphenylenes.

In this work, we compare for the first time the stability of []cycloparaphenylene ([]CPP)-based host-guest complexes with Li@C and C in the gas and the solution phase. Our gas-phase experiments reveal a significant increase in stability for the complexes featuring [9-12]CPP with Li@C. This increased interaction strength is also observed in solution. Isothermal titration calorimetry shows for the formation of [10]CPP⊃Li@C a two orders of magnitude larger association constant than that for the C analog. Additionally, an increased binding entropy is observed. This study contributes to a better understanding of host-guest complexes between []CPPs and endohedral metallofullerenes at a molecular level, which is the prerequisite for future applications.