Visual chiral recognition of aromatic amino acids with (S)-mandelic acid-based ionic liquids via complexation

• Published in: Talanta (Oxford) Vol. 217; p. 121083
• Main Authors: Ma, Xiaofei, Du, Yingxiang, Zhu, Xinqi, Yang, Jiangxia
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-09-2020
• Subjects: Amino acids; Amino Acids, Aromatic - analysis; Chiral ionic liquids; Complexation; Enantioselective precipitate; Ionic Liquids - chemical synthesis; Ionic Liquids - chemistry; Mandelic Acids - chemical synthesis; Mandelic Acids - chemistry; Molecular Structure; Recognition mechanism; Stereoisomerism; Visual chiral recognition; TMA-CP; Amino acids; PHE; PRO; PHG; CILs; CIL2; CIL1; Visual chiral recognition; FTIR; TRY; EA; GC; Enantioselective precipitate; Complexation; e.e. value; CE; Chiral ionic liquids; TYR; Recognition mechanism; TGA; ILs; NMR; HIS; ARG; LC; SEM
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2020.121083

Recently, chiral ionic liquids have attracted increasing attention in analytical chemistry. However, only a few papers focus on the application of them in visual chiral recognition. Herein, two functionalized chiral ionic liquids derived from (S)-mandelic acid (1-butyl-3-methylimidazolium mandelate, CIL1 and N-butyl-N-methylpyrrolidinium mandelate, CIL2) were prepared for visual chiral recognition of aromatic amino acids for the first time. In the presence of Cu(II) and appropriate solvents, visual enantiomeric responses of phenylalanine, tryptophane, tyrosine and phenylglycine were observed. Relying on solubility or color differences, all chiral recognition could be finished within 5 min. The potential mechanism was investigated by means of infrared spectroscopy, ultraviolet spectroscopy, thermal gravity analysis, elemental analysis and scanning electron microscope. Results revealed that CuSO4 interacted with CIL1 and D-tryptophane in the ratio of 1:1.96:0.43 in relevant precipitate, and the different stability of complex was responsible for the chiral recognition. In addition, resolution of racemic tryptophane was performed, which offered excellent enantiomeric excess values (94.2% for CIL1 and 95.1% for CIL2 in solid phase). The proposed ionic liquids had strong enantioselectivity for aromatic amino acids and great potential in visual chiral recognition.
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•The mandelic acid-based ILs were originally exploited for visual chiral recognition.•Four amino acids enantiomers were visually identified within a short time.•The different stability of complex was responsible for the chiral recognition.•Racemic tryptophane was separated with high resolution efficiency.