Chiral distinction of phenyl-substituted ethanediol enantiomers by measuring the ion mobility of their ternary complexes

Abstract

The distinction of enantiomers is increasingly critical in scientific research and chemical industries, because of their differences in the molecular structure and properties. R/S-Phenyl-1,2-ethanediol (PED), R,R/S,S-Hydrobenzoin (HB), and R/S-1,1,2-Triphenyl-1,2-ethanediol (TPED) are representative aromatic alcohol catalyst-class enantiomers, which directly affect the type and yield of reactants, that their chiral distinction and separation are important. In this work, the three groups of the enantiomers are recognized by measuring the ion mobility spectrometry (IMS) difference of their ternary complexes, which formed by simple non-covalent interaction with chiral selectors and metal ions. Their ion mobility was detected using trapped ion mobility spectrometry-mass spectrometry (TIMS-MS). Different chiral selectors include α-, β-, γ-Cyclodextrins (CDs), rifamycin (Rif), and natamycin (Nat) etc were investigated, and different metal ions were studied as ligands. Interestingly, the target enantiomers could not interact with the chiral selectors directly, but with the addition of metal ions, the ternary complexes of enantiomers-chiral selectors-metal ions can be formed. The mobility results reveal that the peak to peak resolution (Rp-p) was increased with the number of their benzene rings goes, which can up to 2.08. Simply, R/S-PED enantiomers can be successfully distinguished by measuring the IMS of the formed ternary complexes of [β-CD + PED + Cr-2H]+; R,R/S,S-HB enantiomers can be distinguished by measuring the IMS of [Rif + HB + Ba-H]+ and [Rif + HB + Ca-H]+; And R/S-TPED enantiomers can be distinguished by measuring the IMS of [Nat + TPED + Mn-H]+, [Nat + TPED + Co-H]+, [Nat + TPED + Mg-H]+, [Nat + TPED + Ca-H]+, [Nat + TPED + Ba-H]+ and [α-CD + TPED + Al-2H]+, respectively. Moreover, the tandem mass spectrometry experimental results showed that the binding stability of the R- and S-enantiomer ternary complexes has obvious difference and is related to different metal ion, indicating the ternary enantiomer complexes have different rigid structures. In addition, the relative quantification of R/S-enantiomer complexes were performed, good linear coefficient (R2) greater than 0.99 was obtained. The method based on IMS analysis can represent an effective approach for the distinction of phenyl-Substituted ethanediol enantiomers, and the CDs, Rif, Nat can be promising chiral selectors for enantiomers distinction.