A novel metastable-state photoacid for reversible protonation of strong bases.

Metastable-state photoacid (mPAH) has become a common tool for controlling and driving chemical processes with light. However, previously developed mPAHs could not be used for reversible protonation of strong bases, including many common amines and heterocycles. In this work, we developed a novel mPAH using benzimidazole as the structural moiety with the active proton.