Characterization of Inclusion Complexation in Solution State

Techniques like polarography, conductivity measurement and polarimetry can be used to characterize inclusion complex in solution. 

Polarography measures the electron distribution of guest molecule. Specific rotation, which is an inherent property of the optically active species, is measured by polarimetry, as it may be affected by complex formation. Solution conductivities are vividly affected by inclusion complex formation with cyclodextrins. 

In solubility studies, changes in solubility of the guest are plotted as a function of the cyclodextrin concentration if the solubility of a potential guest increases with increasing cyclodextrin concentration, complex formation in solution is indicated [56]. 

Furthermore, C-NMR spectroscopy can also be used to gain insight into the inclusion modes of inclusion complexes in aqueous solution. The cyclodextrin-induced change in the chemical shift results predominantly from the electrical environment effect of the cyclodextrin cavity [59]. 

2 Electron Spin Resonance (ESR) Complexation with radicals in aqueous solutions can be investigated by ESR. The hyperfine coupling constant of radicals is known to be sensitive to the polarity of the medium. If the hyperfine coupling constant alters, the movement of a radical to an environment less polar than water is indicated and confirms the inclusion complex formation [55]. 

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