Manifesting Subtle Differences of Neutral Hydrophilic Guest Isomers in a Molecular Container by Phase Transfer

• Published in: Angewandte Chemie International Edition 2016-07, Vol.55 (29), p.8249-8253
• Main Authors: Lee, Hyun Hee L., Lee, Jong Wha, Jang, Yoonjung, Ko, Young Ho, Kim, Kimoon, Kim, Hugh I.
• Format: Article
• Language: English
• Subjects: Ammonium; Cations; Chemistry; Containers; cucurbituril; Differentiation; gas-phase chemistry; host-guest systems; Isomers; mass spectrometry; Monosaccharides; Solvation; Supramolecular compounds
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201601320

Achieving strong host–guest interactions between synthetic hosts and hydrophilic guests in solution is challenging because solvation effects overwhelm other effects. To resolve this issue, we transferred complexes of cucurbit[7]uril (CB[7]) and monosaccharides to the gas phase and report here their intrinsic host–guest chemistry in the absence of solvation effects. It was observed that effective host–guest interactions in the gas phase mediated by ammonium cations allow the differentiation of the monosaccharide isomers in complex with CB[7] upon vibrational excitation. The potential of the unique observation was extended to a quantitative supramolecular analytical method for the monosaccharide guests. The combination of host–guest chemistry and phase transfer presented in this study is an effective approach to overcome current limitations in supramolecular chemistry. Mass spectrometry (MS) and phase transfer was used to distinguish between complexes of curcurbit[7]uril and four isomeric monosaccharides in the gas phase. The sensitivity of MS enabled a quantitative analysis of monosaccharide concentrations, and this method could be applied to a variety of other host–guest systems.