In Situ Probing and Identification of Electrochemical Reaction Intermediates by Floating Electrolytic Electrospray Mass Spectrometry

The in-depth study of electrochemical (EC) synthesis can require a powerful mass spectrometry (MS) analytical platform which can discover and identify fleeting intermediates in EC reactions. Here we report a floating electrolytic electrospray ionization (FE-ESI) strategy that can perform EC processes in a floating electrolytic cell and monitor intermediates by high-resolution MS. Compared with previous EC-MS methods, a significant advantage of FE-ESI-MS is that it allows one to modulate the electrolytic and electrospray process individually, ensuring its high sensitivity in discovering intermediates and universality to investigate redox reactions in different scenarios. This powerful platform has been successfully used to investigate the EC reductive coupling of p-tolylboronic acid and p-nitrotoluene. A series of nitrene intermediates were discovered and identified by FE-ESI-MS, indicating that a hidden mechanism involving nitrene formation might play a key role in EC reductive coupling process.

Automated summary

In this study, a floating electrolytic electrospray ionization (FE-ESI) strategy was developed to perform electrochemical reactions and monitor intermediates using high-resolution mass spectrometry. Compared to previous methods, FE-ESI-MS allows individual modulation of electrolytic and electrospray processes, ensuring high sensitivity in detecting intermediates and universality in investigating redox reactions. This platform was successfully used to investigate the EC reductive coupling of p-tolylboronic acid and p-nitrotoluene, revealing the presence of nitrene intermediates and suggesting a potential mechanism involving nitrene formation in the EC process.