Density functional study on ionic liquid of 1-propyl-4,5-dibromo-3-methylimidazolium bromide

► The bromine substituted imidazolium-based ionic liquid was investigated by DFT. ► The hydrogen bondings are formed between H2 atoms of cations and Br−. ► The halogen bondings are formed between imidazolium ring substituted bromine atoms and Br−.