Double encapsulation of C₆₀, [6]CPP and Li⁺@C₆₀ inside a peropyrene-linked, CPP-based double nanohoop.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Peropyrene-linked and cycloparaphenylene (CPP)-based double nanohoops typically form 1:1 complexes with C60 due to solid-state packing.
• Previous studies indicate that the inherent structure hinders the formation of 1:2 complexes.

Purpose of the Study:

• To provide evidence for the formation of elusive 1:2 complexes between a double nanohoop and C60.
• To investigate the complexation behavior with [6]CPP and cationic endohedral metallofullerenes Li+@C60.
• To explore the binding capabilities of the double nanohoop beyond 1:1 complexation.

Main Methods:

• Electrospray ionization mass spectrometry (ESI-MS) was employed to detect and confirm complex formation.
• Proof-of-concept experiments were conducted to generate and characterize the target complexes.
• Analysis focused on observing ring-in-ring architectures and host-guest interactions.

Main Results:

• The formation of the elusive 1:2 complex between the double nanohoop and C60 was confirmed via ESI-MS.
• A novel binary 1:2 ring-in-ring complex of the double nanohoop with [6]CPP was observed for the first time.
• A stable 1:2 host-guest complex accommodating cationic Li+@C60 was successfully generated, overcoming Coulombic repulsion.

Conclusions:

• The intrinsic binding capability of the double nanohoop host is not limited to 1:1 complexation, contrary to previous assumptions.
• Solid-state packing effects, rather than intrinsic binding limits, constrain the formation of doubly occupied architectures.
• Rational crystal engineering strategies may unlock access to such doubly occupied supramolecular architectures in condensed phases.