Theoretical inclusion of deprotonated 2,4-D and dicamba pesticides in ß-cyclodextrin

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

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.

Current Status of Quantum Chemical Studies of Cyclodextrin Host-Guest Complexes

This article aims to review the application of various quantum chemical methods (semi-empirical, density functional theory (DFT), second order Møller-Plesset perturbation theory (MP2)) in the studies of cyclodextrin host-guest complexes. The details of applied approaches such as functionals, basis sets, dispersion corrections or solvent treatment methods are analyzed, pointing to the best possible options for such theoretical studies. Apart from reviewing the ways that the computations are usually performed, the reasons for such studies are presented and discussed. The successful applications of theoretical calculations are not limited to the determination of stable conformations but also include the prediction of thermodynamic properties as well as UV-Vis, IR, and NMR spectra. It has been shown that quantum chemical calculations, when applied to the studies of CD complexes, can provide results unobtainable by any other methods, both experimental and computational.

Pesticide remediation with cyclodextrins: a review

The aim of this review is to highlight and provide an update on the current development of pesticide remediation methods, focusing on the utilization of different cyclodextrin (CD) molecules. Because of less environmental impact and non-toxic nature, CDs are beneficial for pesticide remediation, reducing environmental risk and health hazards. They are advantageous for the removal of pesticides from contaminated areas, as well as for better pesticide formulation and, posing significant effects on the hydrolysis or degradation of pesticides. The review focuses on the current trend and innovations regarding the methods and strategies employed for using CDs in designing pesticide remediation. Nowadays, in addition to the conventional experimental techniques, molecular simulation approaches are significantly contributing to the study of such phenomena and hence are recognized as a widely used tool.

Evaluation of the molecular inclusion process of β-hexachlorocyclohexane in cyclodextrins

The present work aimed to study the guest-host complexes of β-hexachlorocyclohexane (β-HCH), a pesticide with high environmental stability that can cause severe health problems, with the most common cyclodextrins (α-, β-, and γ-CDs). The formation reactions of these molecular inclusion complexes were addressed in this research. The multiple minima hypersurface methodology, quantum calculations based on density functional theory and a topological exploration of the electron density based on the quantum theory of atoms in molecules approach were used to characterize the interaction spaces of the pollutant with the three CDs. Additionally, charge distribution, charge transfer and dual descriptor analyses were employed to elucidate the driving forces involved in the formation of these molecular inclusion complexes. Three types of fundamental interactions were observed: total occlusion, partial occlusion and external interaction (non-occlusion). Finally, experiments were performed to confirm the formation of the studied complexes. The most stable complexes were obtained when γ-CD was the host molecule. The interactions between the pesticide and CDs have fundamentally dispersive natures, as was confirmed experimentally by spectroscopic results. All the obtained results suggest the possibility of using CDs for the purification and treatment of water polluted with β-HCH.