Probing inclusion complexes of 2-hydroxypropyl-β-cyclodextrin with mono-amino mono-carboxylic acids: physicochemical specification, characterization and molecular modeling

Density (ρ), viscosity (η) and surface tension (γ) of three amino acids (valine, alanine, and glycine) have been measured at a different mass fraction (0.002 - 0.009) of aqueous hydroxypropyl-β-cyclodextrin (HPβCD) mixtures and different temperatures (278.15 - 295.15 K). The formation of inclusion complexes has been analyzed via evaluating the amounts of apparent and limiting apparent molar volumes, limiting apparent molar expansibilities, activation energy, kinematic, relative, intrinsic, spatial, and dynamic viscosities. The surface tension studies indicated that the inclusion complexes have been formed with 1:1 stoichiometry and mediated by hydrophobic effects and electrostatic forces. Additionally, the ρ and η parameters were evaluated by molecular modeling experiments to provide more details on the mechanisms of the complexation.