A computational study on the enantioselective separation of cyhalothrin enantiomers by β-cyclodextrins

Context

This computational study investigates the enantioselective separation of λ-cyhalothrin (CLT) enantiomers, ( +)-[S]-CLT and ( −)-[R]-CLT, using native β-cyclodextrin (β-CD) and its sulfated derivative (S-β-CD) as chiral selectors. Our calculations, employing B97D/6-31G(d,p)//PM3 and B97X-D3/6-31G(d,p)//GFN2-xTB methodologies, consistently demonstrate that the ( −)-[R]-CLT enantiomer forms more stable inclusion complexes with both selectors, predicting a longer migration time compared to ( +)-[S]-CLT. This enhanced stability is primarily due to favorable hydrophobic interactions, with additional hydrogen bonding contributing in the case of S-β-CD. S-β-CD exhibited superior separation efficiency, as evidenced by higher ΔΔG values, likely due to structural modifications induced by sulfate groups that optimize steric fitting and van der Waals interactions within the cyclodextrin cavity. These findings highlight the potential of S-β-CD for efficient enantiomeric separation of CLT and underscore the utility of computational chemistry in understanding chiral recognition mechanisms.

Methods

Two distinct theoretical methodologies, B97D/6-31G(d,p)//PM3 and ωB97X-D3/6-31G(d,p)//GFN2-xTB, were employed to elucidate the structural and energetic properties of these diastereomeric complexes. The calculations were performed on Gaussian 09 and ORCA 5.0 software packages.