This study reveals that the effect of anion structures on solvent-solute interactions by analysis of sophisticated thermophysical properties of ionic liquids (ILs) with molecular solvent. Three imidazolium based ILs (1-octyl-3-methylimidazolium) [Omim][NTf2], [Omim][PF6] and [Omim][SCN] were synthesized, characterized and measured the thermophysical properties such as density (ρ) sound speed (u) and viscosity (η) of all ILs with DMF as solvent for binary mixture at various conditions. Furthermore, various derived thermophysical properties (Formula presented.), κs,Φ, (Formula presented.) and ηr, were calculated from experimental data. The type of interactions such as IL-IL or IL-solvent or solvent-solvent are occurred among the component molecules were estimated from the empirical parameters and COSMO−Rs computational study. The obtained results show that the size of anion is governing the volumetric, acoustic and viscometric properties of the studied ILs with DMF. © 2021 Wiley-VCH GmbH