Capture and identification of the electrogenerated picosecond intermediates by mass spectrometry

Probing and identification of the reactive intermediates in electrochemical transformations is essential for gaining in-depth insights into their reaction mechanisms. However, due to their extremely short lifetimes, characterizing the electrogenerated transient species remains a significant challenge for currently available techniques. In this work, we report the first mass spectrometric identification of the electrogenerated transient nitrenium ions (R₂N⁺) and oxenium ions (R-O⁺), whose lifetimes in solutions are as short as picoseconds. This achievement is made possible by the fabrication of a dual-function hybrid ultramicroelectrode/ion emitter, which permits the in-situ generation and rapid transferring of the fleeting intermediates into the gas phase for mass spectrometric analysis. For the first time, a series of previously hypothetical nitrenium/oxenium ions, including the long-sought glycosyl cations, were directly probed using mass spectrometry. Additionally, we also propose a viable mechanism involving the stabilizing effects of the positively charged microdroplets to explain the capture of the transient intermediates.