Inclusion complexation of imidazolium-based ionic liquid and β-cyclodextrin: A detailed spectroscopic investigation

Host-guest inclusion complexation (IC) behavior of ionic liquid (IL) 1-decyl-3-methylimidazolium tetrafluoroborate [Dmim][BF4] within β-cyclodextrin (β-CD) and the nature of complexation as well as binding affinity were studied in aqueous solution with the help of different spectroscopic methods i.e., fluorescence, dynamic light scattering (DLS), UV–vis, FTIR, and 1H NMR spectroscopy. The nature of complexation has been established from the results obtained for critical micelle concentration (cmc), aggregation number (Nagg), Stern-Volmer constant, particle size. Fluorescence and UV–vis studies revealed that 1:1 M stoichiometry of the ICs, while FTIR and DLS studies show the formation of H-bonding, electrostatic, hydrophobic interactions within the system and size of ICs formed. IL [Dmim][BF4] imparts distinctive properties of the ICs along with the instantaneous presence of vesicle and micelle which is well supported by DLS results. Binding constants for β-CD and [Dmim][BF4] complexes have been derived using Benesi-Hildebrand method and the thermodynamic properties have been evaluated with the help of van't Hoff equation. 1H NMR results are significant to show the changes for chemical shift of the β-CD and [Dmim][BF4] complexes which reveals that alkyl part of the IL is inserted into the hydrophobic cavity of β-CD. The obtained results on the ICs of [Dmim][BF4]/β-CD in this article can find potential application in soft matter construction, sensing and drug delively.