Supramolecular host-guest complexation with excellent comparison among three similarly substituted ionic liquids, namely, 1-butyl-3-methylimidazolium chloride, 1-butyl-4-methylpyridinium chloride and 1-butyl-1-methylpyrrolidinium chloride have been investigated with 18-crown-6 in acetonitrile medium by conductivity in a range of temperature to elucidate the stoichiometry of the complexes. The programmed mathematical study with the help of conductivity data provides association constants for the complexes, by which the thermodynamic properties have been evaluated for improved understanding about complexation. The molecular interactions have been explained and critically discussed with the help of FT-IR and H-1 NMR spectroscopic studies, which illustrate H-bond and ion-dipolar attractions primarily exist in complexation. (C) 2017 Elsevier B.V. All rights reserved.