Complex Formation of Ag+ and Li+ with Host Molecules Modeled on Intercalation of Graphite

TL;DR

This paper explores how Ag+ and Li+ ions interact with specially designed host molecules based on xanthene and pyrene to mimic interactions with graphene.

Contribution

The study introduces new host molecules to model cation–π interactions and compares their complexation behavior with metal ions.

Findings

Stacked host molecules showed stronger interactions with metal ions compared to individual pyrene.

Ag+ had moderate coordination ability with the box-shaped host, while Li+ interaction was weak.

Intercalation is more likely in the stacked compound due to greater structural flexibility.

Abstract

Pi-stacked and box-shaped host molecules with xanthene as the basis and pyrene as the π-plane were synthesized to verify cation–π interactions between graphene and metal cations. Since crystal structure analysis was not available, DFT calculations were performed to determine the optimized structure, and the π-planes were found to have a slipped parallel structure, with average distances of 456.2–581.0 pm for the stacked compound and 463.4–471.4 pm for the box-shaped compound. Li+ and Ag+ were chosen as acceptors for complexation with metal ions, and their interactions with the π-plane were clarified by NMR titration. Clearly, the interaction with metal ions increased when pyrene π-planes were stacked rather than the pyrene itself. In the stacked compound, the association constants of Ag+ and Li+ were similar; however, in the box-shaped host molecule, only Ag+ had moderate coordination ability, but the interaction with Li+ was very weak, comparable to the interaction with pyrene. As a result, intercalation is more likely to occur in stacked host compound 1, which has some degree of freedom in the pyrene rings, than in the box-shaped compound.

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