A molecular Popeye: Li+@C60 and its complexes with [n]cycloparaphenylenes

In this work, we compare for the first time the stability of [n]cycloparaphenylene ([n]CPP)-based host-guest complexes with Li+@C-60 and C-60 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-60. This increased interaction strength is also observed in solution. Isothermal titration calorimetry shows for the formation of [10]CPP superset of Li+@C-60 a two orders of magnitude larger association constant than that for the C-60 analog. Additionally, an increased binding entropy is observed. This study contributes to a better understanding of host-guest complexes between [n]CPPs and endohedral metallofullerenes at a molecular level, which is the prerequisite for future applications.

Automated summary

In this study, the stability of [n]cycloparaphenylene (nCPP)-based host-guest complexes with Li+@C-60 and C-60 was compared for the first time in both gas and solution phases. Results showed a significant increase in stability for the complexes featuring [9-12]CPP with Li+@C-60, which was also observed in solution. The formation of [10]CPP superset of Li+@C-60 exhibited a two orders of magnitude larger association constant compared to the C-60 analog, along with an increased binding entropy. This research contributes to a better understanding of host-guest complexes between [n]CPPs and endohedral metallofullerenes at a molecular level.