How the cation–cation π–π stacking occurs: A theoretical investigation into ionic clusters of imidazolium

•The nature of non-covalent interaction between cation–cation π–π stacking is explored theoretically.•Such interaction is different to common π–π interaction.•The occurrence of the interactions is attributed to a few contacts of CH and halide.

The cation–cation π–π stacking is uncommon but it is essential for the understanding of some supramolecular structures. We explore theoretically the nature of non-covalent interaction occurring in the stacked structure within modeled clusters of 1,3-dimethylimidazolium and halide. The evidences of the energy decomposition analysis (EDA) and reduced density gradient (RDG) approach are different from those of common π–π interaction. Isosurfaces with RDG also illustrate the strength of the titled π–π interaction and their region. Additionally, we find that the occurrence of this interaction is attributed to a few CH···X interactions, as depicted using atom in molecule (AIM) method. This work presents a clear picture of the typical cation–cation π–π interaction and can serve to advance the understanding of this uncommon interaction.

Graphical abstractReduced density gradient isosurface map (left) and atom in molecule (right) of the intermolecular interactions in the [Br][DMIM]···[DMIM][Br] dimmers.Figure optionsDownload full-size imageDownload high-quality image (188 K)Download as PowerPoint slide