The interaction of a CO2 molecule with different anions commonly used in room temperature ionic liquids (RTILs) has been studied under isolated conditions. Minimum energy structures obtained using density functional theory based calculations suggest the dominance of Lewis acid-base interactions between the species. In the optimized configurations, the CO2 molecule is found to adopt a non-linear geometry. The extent of the consequent split in the CO2 bending mode calculated from a Hessian analysis agrees qualitatively with vibrational spectroscopic results. The implication Of CO2-anion interaction to the solubility Of CO2 in RTILs is discussed. (C) 2007 Elsevier B.V. All rights reserved.