Spectral study on inclusion interaction and enantiorecognition of 2‐aryl carboxylic acids with hydroxypropyl‐β‐cyclodextrin

Abstract

The inclusion interaction between hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) and 21 2‐aryl carboxylic acids was investigated by UV (ultraviolet) spectrophotometer. The inclusion constant of each 2‐aryl carboxylic acids with HP‐β‐CD was determined by Benesi–Hildebrand's equation. According to our previous work, it was found that a high inclusion constant for inclusion complex formed by a racemate and cyclodextrin was always observed with the fact that a high enantioseparation factor was achieved for the racemate in enantioseparation by liquid–liquid chromatography, which suggested that high binding combination between racemate and cyclodextrin is very important for a successful enantioseparation in enantioselective liquid–liquid extraction. Among all the studied subjects, mandelic acid enantiomer, 2,3‐diphenylpropionic acid enantiomer, and naproxen enantiomer were selected for the further study. The inclusion constants of enantiomers of these three subjects were determined by UV spectra, which indicated that a necessary difference in inclusion constants between enantiomer and cyclodextrin was also essential. It was found in UV spectra that the absorbance of the analytes with the addition of cyclodextrin would increase or decrease, which was determined by the type of electron excitation. The conformation changes of small molecules can lead to the changes of chromophore valence electron clouds distribution, causing the HOMO‐LUMO energy difference decreased. Thus, a red shift of the wavelength of the maximum absorption was produced indicating that the possibility of the molecular interaction of enantiomers with HP‐β‐CD exists.

Supramolecular Interaction Modulation in Thermosensitive Composites: Enantiomeric Recognition and Chiral Site Regeneration

“…The enantiomeric recognition of chiral sites is the basis of chiral molecular separation systems. Chiral materials with enantiomeric recognition functions, such as cyclodextrin and their derivatives, − macrocyclic aromatic hydrocarbons, two-dimensional skeletal materials, − and chiral ionic liquids (ILs), , have been reported. Enantiomeric recognition is realized by the presence of enantiomers with different affinities to the chiral site based on different noncovalent interactions between the chiral site and enantiomers. ,, The chiral site can act as a host molecule and the enantiomer as a guest molecule during enantiomer recognition by cyclic chiral materials such as cyclodextrins .…”

Advantages of Induced Circular Dichroism Spectroscopy for Qualitative and Quantitative Analysis of Solution-Phase Cyclodextrin Host–Guest Complexes

“…UV spectroscopy [ 13 ] is also often used because it is fast, is cheap, requires relatively small samples, and has usually good sensitivity. Its drawbacks include the need for the presence of a chromophore and the need for a change in the electron distribution of the chromophore group and the energy difference between the HOMO and LUMO orbits due to the interaction with cyclodextrin.…”