Theoretical Study on Enantioselectivity of α - and γ –cyclodextrin Towards Baclofen Enantiomers

The purpose of this study is to report the quantum chemical study of enantioselectivity of a-cyclodextrin (a-CD) and g -cyclodextrin (g -CD) towards baclofen enantiomers. In this regard, host-guest interactions of a -CD and g -CD with baclofen enantiomers were simulated using DFT (B3LYP/6-31G(d)) method with water as solvent. The Natural Bond Orbital (NBO) for the direction and magnitude of charge transfer interactions was calculated. Furthermore, the Quantum Theory of Atoms in Molecules (QTAIM) was employed to indicate the existence and the relative strength of the intermolecular bonds. The investigations revealed that the interaction energies of R-baclofen with a-CD and g -CD were more negative than those of S ones. The interaction energies of a- and g -CD with baclofen enantiomers with the NBO indicate the most significant charge transfer occurs for the O atom lone pair of CDs to the O-H anti bond of the baclofen also interactions between baclofen and other atoms of CDs is slight. The QTAIM results show the non-covalent interactions of the baclofen with CDs with electrostatic effects. The overall theoretical data corroborate with experimental results.