Study of complexation of an ionic liquid inside into crown ethers in aqueous environments by physicochemical techniques

Inclusion complexation between crown ethers (CEs) (viz., 15-crown-5, 18-crown-6) and an ionic liquid (IL) (viz., 1-ethyl-3-methylimidazolium tosylate) in aqueous medium have been demonstrated by conductivity, surface tension and 1Proton Nuclear Magnetic Resonance (H NMR) study. The results show the formation of 1:1 complexes between CEs and the IL through electron-deficient imidazolium cation and electron pairs of oxygen atoms of the CEs. Hydrogen bonding is the key factor responsible for complexation, while, the ion–dipole interactions also contribute towards the complex formation. The formation constants have been derived from conductivity study and the complexes have been analysed by 1H NMR study.