Real-time Monitoring of Photoinduced pH-jumps by In Situ Rapid-scan EPR Spectroscopy

This work represents the first demonstration of a light-induced pH-switchable process monitored by in situ rapid-scan (RS) electron paramagnetic resonance (EPR) spectroscopy on the millisecond timescale. Here, we investigate the protonation state of an imidazoline type raical as pH sensor under visible light irradiation of a merocyanine photoacid in bulk solution. The results highlight the utility of photoacids in combination with pH-sensitive spin probes as an effective tool for real-time investigation of biochemical mechanisms regulated by changes of the pH value.