# 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.

## Key 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.