Spectroscopic studies on the inclusion complexation of valine enantiomers with B-cyclodextrin / Nurul Yani Rahim, Goh Soen Qeng and Nur Qausar Md Saad

Complexes of B-cyclodextrin (B-CD) with amino acid analytes such as valine are an ideal study of molecular recognition since L- and D-forms of valine are differently adsorbed on the chiral surface of the B-CD molecule in the aqueous phase. Therefore, the inclusion complex formation of valine enantiomers is extensively studied using spectroscopy methods to better understand the characteristics of the inclusion complexes. Hence, FTIR and UV spectroscopy were utilized to investigate the inclusion complexes formed by the enantiomers L-valine and D-valine in an aqueous solution with B-CD. According to the FTIR spectra, the differing relative intensities and characteristic band shifts of the two enantiomers show that they have different interactions when they are complexed with B-CD. Experiments with the FTIR spectrometer indicated a discernible decrease of the C-O stretching and ring deformation, both of which point to the embedding of valine into the B-CD cavity. In neutral pH, it seems that there is a significant difference in absorbance for the L- and D-valine complexes B-CD. The Benesi-Hildebrand plot was used to determine the stoichiometry ratio as well as the binding constant of the inclusion complexes. The inclusion complex involving B-CD and the enantiomer of valine had a stoichiometry ratio of 1:1. L-valine has a binding constant of 4922.47 M-1, which is higher than that of D-valine, which is 1010.67 M-1. Based on these findings, it appeared that L-valine had a strong interaction with the cavity of B-CD. According to the findings, the enantioselective reaction has been developed into an analytical method for determining enantiomeric excess via spectroscopic studies.