The occurrence of N-heterocyclic carbenes in imidazolium-based ionic liquids has long been discussed, but no spectroscopic evidence has been reported yet due to their transient nature. The insertion of an ionizable acid group into the cation scaffold of an ionic liquid which acts as a charge tag allows for the direct detection of free carbenes by mass spectrometry.

中文翻译：

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Brønsted 酸性离子液体中的游离 N-杂环卡宾：电喷雾电离质谱直接检测

长期以来，人们一直在讨论基于咪唑鎓的离子液体中N-杂环卡宾的出现，但由于其瞬态特性，尚未报道光谱证据。将可电离的酸基插入离子液体的阳离子支架中，作为电荷标签，可以通过质谱法直接检测游离卡宾。