Chiral Molecular Recognition Based Onβ-cyclodextrin Ternary System

Chapter1:Firstly, the concept and inclusion complexs of cyclodextrins, and their applications in analytical chemistry are introduced briefly. Then, the chiral discrimination including the discrimination mechanism, involved techniques and common chiral selectors are reviewed. Finally, the research background and main contents of the thesis are outlined simply.Chapter2:Propranolol (PPL) enantiomers possess strong room temperature phosphorescence (RTP) in β-cyclodextrin (β-CD) system in the presence of bromocyclohexane (BrCH) under ambient conditions. The effects of pH, concentration of β-CD and BrCH on the RTP of PPL enantiomers have been investigated in detail. Time-resolved RTP spectroscopy shows that both PPL enantiomers exhibit bi-exponential decay pattern with lifetimes of τi=19.75±1.42and τ2=1.78±0.09ms for R-PPL, and τ1=14.14±1.36and τ2=1.34±0.07ms for S-PPL. The lifetime differences between these enantiomers are△τ=5.61and△τ2=0.44ms, indicating that chiral discrimination of PPL enantiomers can be achieved in β-CD/BrCH system. In addition, the chiral discrimination mechanism was investigated based1H NMR and2D NMR experiments. The chiral discrimination of R-and S-PPL is realized via their difference in interaction with the chiral cavity of β-CD due to their difference in stereochemical structure. Finally, molecular modeling was done for propranolols to investigate interaction mechanism with β-CD on a molecular level, the results of molecular modeling simulation are consistent with the experimental behavior.Chapter3:In the presence of different linear and branched alcohols, the chiral recognition of w-CD to R,S-propranolol (PPL) has been investigated by fluorescence probe spectroscopy. The effects of various alcohols on the chiral discrimination of R,S-PPL/β-CD have been examined based on the inclusion constants and quenching constants. Experimrntal results demonstrated that the binding constants and quenching constants of E,S-PPL/β-CD were affected dramatically with the addition of alcohol as the third component, and leading to the chiral selection enhanced. The effects of alcohols in order were the Isobutyl alcohol> Isopropyl alcohol> n-Butanol>1-pentanol> Isoamyl alcohol> Cyclohexanol>1-propanol. Furthermore, the hydrogen-bonding interaction between alcohols and β-CD was proposed to explain the essence of interaction.Chapter4:Naproxen was used as a spectral probe to study the interaction of six kinds of alcohols and R,S-Naproxen/β-CD complex by steady-state fluorescence measurements. The effects of alcohols in order were the n-Butanol> Isoamyl alcohol>1-pentanol>1-propanol> Isobutyl alcohol> Isopropyl alcohol. Besides, the enantioselective resolution of naproxen enantiomers by high performance liquid chromatography with (3-CD as a chiral mobile phase additive and C18silicagel column as separation stationary phase is builded, the effects of different alcohols on the resolution was investigated. The results of two methods showed that the presence of alcohols has affected on the inclusion and complexes of cyclodextrins with select guest molecules, and the hydrogen-bonding interaction between alcohols and (3-CD leads to formation of the ternary complexes.