Theoretical study of β and γ-cyclodextrins inclusion complexes with nineteen atropisomeric polychlorobiphenyls

Abstract

Inclusion complexes of β and γ-cyclodextrins (CDs), chirally selective macrocycles, with 19 atropisomeric polychlorinated biphenyls (PCBs), stable at physiological temperatures, were studied by molecular mechanics optimized potential for liquid simulations and semi-empirical quantum AM1 methods. Bimodal manual docking, geometry optimization and single point calculations were done. PCB:CD complex formation was studied considering two ways of entry in the large base of CD cavity: with biphenyl C1–C1′ bond axis of PCBs oriented parallel and anti-parallel with the CD trunk height axis. A distance dependent dielectric constant was used to account for the solvent effect. The values of complexation and binding energies were calculated, confirming the existence of a specific van der Waals (vdW) type interaction. β and/or γ-CD chiral recognition of the 19 atropisomeric PCBs, is described by means of the complexation and binding energy values. The binding energy is a better discriminator of PCBs enantiomers than complexation energy considering the average energy differences between (+) and (−) PCB:β/γ-CD complexes. The chromatographic elution order of several PCB enantiomers from literature was correlated with the complexation and binding energies. The molecular modeling of inclusion complexes is recommended to be used as enantiomer identification tool in correlation with chromatographic data.