The cucurbit[n]uril family: prime components for self-sorting systems

Area of Science:

• Supramolecular Chemistry
• Host-Guest Chemistry
• Molecular Recognition

Background:

• Cucurbit[n]urils (CB[n]) are macrocyclic hosts known for their unique cavity structures.
• Understanding the binding affinities and selectivities of different CB[n] homologues is crucial for designing advanced molecular systems.

Purpose of the Study:

• To quantify the binding constants (Ka) for various host-guest complexes involving cucurbit[n]urils (CB[6]-CB[8]).
• To investigate the size, shape, and functional group selectivity of CB[7] and CB[8] compared to CB[6].
• To explore the collective selectivity of the CB[n] family for potential applications in self-sorting systems.

Main Methods:

• 1H NMR competition experiments were employed to determine binding constants.
• UV/vis titration was used to establish absolute binding constants for reference.
• Analysis focused on the interactions between CB[6], CB[7], CB[8], and various adamantane derivatives and other guests.

Main Results:

• CB[7] and CB[8] demonstrate selectivity comparable to CB[6], with CB[7] effectively hosting trimethylsilyl groups.
• Binding constants for CB[7] with adamantane derivatives 22-24 exceeded 10^12 M^-1.
• High collective selectivities were observed, with distinct preferences for CB[7] versus CB[8] depending on the guest structure.

Conclusions:

• The CB[n] family exhibits high individual and collective selectivity, making them valuable for molecular recognition.
• The remarkable binding affinities and selectivities position CB[n] as key components for developing functional biomimetic self-sorting systems.