Inclusion complexation between tetrabutylphosphonium methanesulfonate as guest and α- and β-cyclodextrin as hosts investigated by physicochemical methodology

Abstract

Formation of the inclusion complexes of the ionic solid tetrabutylphosphonium methanesulfonate with α- and β‑cyclodextrin along with its nature, characterization and binding ability was examined in solution and solid state with the help of 1H NMR, 2D-ROESY, surface tension, conductivity, FT-IR and HR-MS studies. Appearance of the cross peaks in the 2D-ROESY spectra and significant shift of signals of H-3 and H-5 protons of both the cyclodextrins and the protons of the guest molecule in the 1H NMR spectra of complex confirmed the phenomena of inclusion. Both the surface tension and conductivity study revealed one single break point suggesting 1:1 stoichiometry of the inclusion complexes. The peaks found in the mass spectra, for both the cases, with m/z value equal to the combined mass of host and guest confirm the 1:1 stoichiometry. Significant binding constants were obtained for both the cases, which supports the higher stability of inclusion complexes. All the above study showed more feasible inclusion in case of α‑cyclodextrin than β‑cyclodextrin.