Quantification of the interactions in halide-anion-based imidazolium ionic liquids

•Quantification of interactions in 20 halide-anion-based imidazolium ILs (Cnmim X, X = Cl, Br, I, and BF4; n = 2, 4, 6, 8, and 10) was studied with dispersion-corrected density functional theory (DFT).•The presence of water and increase of anion size and alkyl chain length, resulting in an enhanced contribution of the dispersion energies.•Strong hydrogen bonding with a partial covalent character was observed between monoatomic anions and the C2-proton of the imidazolium ring.•A clear correlation between stabilization energy (E(2)) and hydrogen bond lengths were observed.