Effect of a Surface‐Active Lonic Liquid on Calixarenes

Abstract

Enormous potential of surface-active ionic liquids (SAILs) in a variety of applications is due to the fact that they possess favorable properties of both ionic liquids and surfactants. Interaction of a SAIL, 1-decyl-3-methylimidazolium chloride ([C10mim][Cl]), with three structurally different calixarenes, (1), (2), and (3), and a fluorophore (dansyl)-appended calixarene (4) within basic aqueous media reveals interesting information. The cmc of [C10mim][Cl] in basic aqueous solution is found to be 13.5 mM. UV–Vis absorbance hints at presence of relatively stronger interaction between [C10mim][Cl] and (1) as compared to (2)/(3). Pyrene fluorescence from micellar [C10mim][Cl] reveals the polarity to increase significantly as concentration of (1) is increased. On the contrary, polarity decreases as concentrations of (2) and (3) are increased. This implies strong interaction of (1) via its nitro functionalities with pyrene; interaction of (2)/(3) is through the organic framework. This is supported by relatively stronger quenching of pyrene fluorescence by (1) as nitro functionality is known to quench pyrene fluorescence. Fluorescence from dansyl-appended calixarene (4) shows hypsochromic shift as the concentration of micellar [C10mim][Cl] is increased. This indicates change in the polarity of dansyl cybotactic region within micellar pseudophase with increasing concentration of [C10mim][Cl]. Site-specific interaction of calixarenes with [C10mim][Cl] within basic aqueous media is amply highlighted by this investigation.