Ground-state intermolecular donor–acceptor complex (MCPNTf 2 -MN; 1:1) is formed between π -electron of 1-methyl-naphthalene (MN) as solute (electron-rich) and π + electron of 1-methyl-4-cyanopyridinium bis((trifluoromethyl)sulfonyl)amide (MCPNTf 2 ) as solvent (electron deficient), observed in solid state. Intermolecular charge-transfer (IMCT) band is observed, indicating the formation of stable MCPNTf 2 -MN complex. The IMCT process of MCPNTf 2 -MN complex depends on relative strength of π – π + stack between cation of MCPNTf 2 IL and aromatic unit of MN. From DFT studies, it is clear that the geometry and interactions in MCPNTf 2 -MN complex are also influenced by NTf 2 anion. This solute–solvent interaction shows the deviation of inertness nature of MCPNTf 2 IL. AIM analysis, electron localization function (ELF) and localized orbital locator (LOL) surface maps are obtained to achieve information regarding intermolecular interactions in the complex. Hirshfeld surface analysis and its fingerprint maps are used to identify pairwise interactions between atoms in order to avail molecular packing of the complexes from crystallographic data. NCI plots display combination of specific atom–atom interactions through hydrogen bond and vdW interactions. AIMD study shows that the complex attains a lower energy of − 2630.72 hartree at 125 and 445 fs.