Conformational preferences of two imidazolium-based ionic liquids at high pressures

► We have investigated the pressure-induced conformational changes of imidazolium-based RTILs. ► The trans conformer of the CNCC angle of the [emim]+ cation becomes predominant at high pressure. ► The conformational change of the CNCC angle of the [bmim]+ cation is independent of pressure. ► The gauche-trans conformer for the butyl cation of the [bmim]+ cation is predominant at high pressure. ► The [emim]+ and [bmim]+ cations cause the respective conformational preferences at high pressures.