Identification of Bi-2-naphthol and Its Phosphate Derivatives Complexed with Cyclodextrin and Metal Ions Using Trapped Ion Mobility Spectrometry.

ABSTRACT

The separation of chiral enantiomers has gained increasing importance in many research fields, becoming a major research hotspot. 1,1'-Bi (2-naphthol) (BINOL) and 1,1'-binaphthyl-2,2'-diyl hydrogen phosphate (BNP) are referred to as atropisomer chiral molecules, which are essential chiral catalysts and intermediates in several reactions. In this work, BINOL and BNP atropisomers are separated and identified using trapped ion mobility spectrometry (TIMS) to monitor the different mobilities of their derivative complexes. The latter are obtained by the simple mixing of BINOL/BNP, cyclodextrin (CD), and the metal ions through noncovalent interactions. The results indicate that the enantiomer complexes of BINOL/BNP can be separated with a certain specificity, showing that R-, S-BINOL can be separated by the ternary complexes of [BINOL+γ-CD + Rb]+, [BINOL+γ-CD + Cu-H]+, and [BINOL+ß-CD + Cu-H]+ based on the difference in their mobility; similarly, the R-, S-BNP enantiomer can be isolated by the formed ternary complexes of [BNP+α-CD + Ba-H]+, [BNP+ß-CD + Co-H]+, [BNP+ß-CD + Ca-H]+, [BNP+ß-CD + Cu-H]+, [BNP+ß-CD + Fe-H]+, [BNP+ß-CD + Li]+, and [BNP+ß-CD + Sr-H]+. Furthermore, the peak separation rate (Rp-p) of the complexes was calculated, with the Rp-p of the three enantiomers of BINOL being 1.130 and the Rp-p of the seven complexes of BNP reaching 2.089. At last, the different survival yields for the collision energies were found for the enantiomer complexes, revealing the rigid structural differences in the stereospecificity of the enantiomer complexes that result in the separation by the TIMS. Additionally, due to the advantages of simple operation, fast speed, and high sensitivity and because chemical derivatization and chromatographic separation are not required, the developed method can provide a promising and powerful strategy for the separation and identification of binaphthyl derivatives or even other enantiomers of the reaction intermediates.