Formation and characterization of β-Cyclodextrin inclusion complexes with 1-Allyl -3 -Methyl dicyanamide ionic liquids

Abstract

This work presents a comprehensive study on the aggregation behaviour and inclusion complexation of 1-allyl-3-methylimidazolium dicyanamide ([Amim]DCA) with β-cyclodextrin (β-CD) in aqueous solutions. A multi-technique approach was used to elucidate the nature of the interactions, including conductivity, ultraviolet–visible (UV–VIS) spectroscopy, dynamic light scattering (DLS), and density and viscosity measurements. Conductivity decreased with increasing β-CD concentration, with a significant dip at 1 mM β-CD, indicating 1:1 host-guest stoichiometry. Thermodynamic parameters derived from density and viscosity data, such as apparent molar volume (V_φ), isentropic expansion coefficient (α_P) and activation energy for viscous flow (E_a), further confirmed the confinement of [Amim]DCA within β-CD. Job's plot analysis and binding constant calculations supported the preferential encapsulation of the DCA⁻ anion inside the β-CD cavity while the [Amim]⁺ cation remained solvated bulk water. FTIR spectroscopy corroborated this inclusion mechanism. DLS and zeta potential measurements showed an increase in particle size and a decrease in surface charge upon the addition of β-CD, consistent with the formation of stable host-guest aggregates. These findings enhance our understanding of the IL-cyclodextrin host-guest complex and support its potential applications in nanostructure engineering and drug delivery.