The interaction of inherently chiral resorc[4]arenes with different chiral ammonium ions was measured by electrospray ionization mass spectrometry. For this purpose, one enantiomer of the ammonium guests was labeled with deuterium to distinguish the enantiomers by their mass. We synthesized the ammonium salts by the reaction of chiral primary amines with either CH3I or CD3I and analyzed the resulting ammonium iodides by nuclear magnetic resonance and optical rotation. The complexation experiments were performed by mixing the chiral host with various ratios of the unlabeled guest and its labeled enantiomer. By analyzing the integrals of the host–guest complexes, we observed a chiral discrimination effect and a secondary isotope effect as well.
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13.
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16.
The “◊”-sign indicates that the guest is labeled by deuterium, i.e. the methyl groups at the nitrogen are perdeuterated.
17.
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18.
The ISIR value is defined in analogy to the IRIS value in References 3 and 4. In contrast to M. Sawada, our ISIR value just reflects the measured signal ratios and the chiral as well as the isotope effect.
