Assessment of the usefulness of β-cyclodextrin in the removal of progesterone from the environment

Abstract

The paper presents the results and interpretation of theoretical calculations for the progesterone–β-cyclodextrin (P@β-CD; G4MP2) and progesterone–β-cyclodextrin–β-cyclodextrin (P@β-CD–β-CD; G2) systems. The geometry of the progesterone molecule was optimized on basis of the DFT theory using the B3LYP, PBE1PBE and M06-2X functionals, for selected Pople basis sets [6-31G, 6‐31++G, 6‐31++G(d,p), 6-311G, 6‐311++G, 6‐311++G(d,p)] and the Dunning basis set (aug-cc-pVDZ). Presented results of theoretical calculations provide insight into the mechanism of formation of supramolecular systems of progesterone and β-cyclodextrin, allowing us to understand the impact of differences in the polarizability of specific fragments of the “guest” molecule, through the analysis of the Mulliken population distribution, on the tendency for equilibrium inclusion by “host” molecules characterized by selective affinity towards hydrophilic and hydrophobic molecular systems. The comparison of model structures of “guest–host” systems with 1:1 and 1:2 stoichiometry allows us to assess the contribution of a given type of non-covalent interactions (hydrogen bonds, van der Waals interactions, London dispersion forces) in the formation of supramolecular complexes. Due to the complexity of the real research object, including interactions between large molecules in solution, in this work it was decided to choose an approximation that reflects only the key effects. The results presented in this paper constitute a starting point for both theoretical research on analogous supramolecular systems based on β-cyclodextrin derivatives, as well as instrumental studies (NMR, FT–IR, HPLC) of preparations of real inclusion complexes. The approach adopted now can contribute to a better understanding of the phenomenon used in the development of water purification technologies.