Investigation of inclusion complexes of ametryne and atrazine with cucurbit[n]urils (n = 6–8) using experimental and theoretical techniques

Inclusion complexes of cucurbit[n]uril, CBn, with atrazine (ATZ) and ametryne (AME) herbicides were investigated in aqueous media and solid state. Mass spectrometry using matrix assisted laser desorption time-of-flight, MALDI-TOF, and ¹ HNMR techniques were used to characterize the inclusion complexes prepared in aqueous media. The solid complexes between the triazine herbicides and CBn hosts were prepared by lyophilization and were characterized by Fourier transform infrared spectroscopy (FT-IR) and powder X-ray diffraction (PXRD) technique. Molecular dynamics (MD) simulations were used to study the mechanism of inclusion and to monitor the stability of these complexes in aqueous media. Analysis of the MD trajectories has shown that both triazines form stable complexes with CBn in aqueous media throughout the simulation time. The stability of these complexes was found to originate from the hydrophobic effects where both hosts prefer to accommodate the nonpolar cavity of the hosts. It was observed that CB6 is capable of encapsulating only the isopropyl side chain of the guests, whereas the other two hosts were able to accommodate the major parts of the guests. A number of strong hydrogen bonds between the hosts and the guests further increased the stability of the complexes.