Cesium is a major fission product in spent nuclear wastes. Crown ethers are used as extracting agent for the removal of cesium ions from aqueous media. We report the interaction energies between the individual complexing species i.e. crown ether and Cs+ metal ion. In order to understand the mechanism of complexation and the behavior of crown ether ligand, crown ether (CE) molecules and Cs+NO3- ions were inserted randomly in the Ionic Liquid-water/methanol biphasic system, where Ionic Liquid is carrier solvent for CE. It was observed that the interaction energies which comprised of the non-bonded interaction during initial stages of the simulation have a value close to zero. This suggests that the Cs+ cation is not present in the crown ether. After the formation of Cs+-CE complex, it is very clear that the electrostatic interactions are particularly attractive in nature and are crucial in realizing complexation. © 2016 The Authors.