Structural, electronic, and thermochemical properties of salicylic acid-containing ionic liquids as active pharmaceutical ingredients

[Display omitted] •DFT calculations to understand the structure and electronic properties of active pharmaceutical ingredient ionic liquids.•The relative orientation of the anions and cations was selective.•The most stable conformations were analyzed by the molecular electrostatic potential (MEP) method.•Cation-anion interaction energy and its relationship with the structure of ionic. Active pharmaceutical ingredient ionic liquids have recently been developed as a new generation of ionic liquids. In this study, the geometrical and electronic structures of six imidazolium-based ionic liquids containing salicylic acid in the cation or/and anion are studied by performing density functional theory calculations. Molecular electrostatic potential surfaces of the cation and anion fragments are obtained to elucidate those sites at which they are most likely to interact. The magnitude of the cation–anion interaction energies is calculated. The natural bond orbital method is performed to analyze the cation–anion interactions. The standard enthalpies of formation of the studied ionic liquids are calculated using the atomization approach. The results indicate a relationship between the enthalpies of formation and the structure of the studied ionic liquids.