did not take place in the reaction system (Fig. ). This observation suggests that a radical polar cross-over process enabled protonation was operational. Subsequently, cyclic voltammetry (CV) experiments were carried out to gain insight into the oxidative process (Fig. ). The blank consisted of 0.1 M n-Bu4NPF6 in CH3CN (black line, Fig. ). Compound 1aa exhibited a broad peak at 1.2 V and displayed the first distinct oxidation peak at 0.76 V in the presence of base. These results indicate that the oxidation of 1aa by the excited state *4CzPIN (E1/2(*P/P -) = 1.35 V vs SCE is thermodynamically feasible , especially in the presence of base. This is also consistent with the fact that the fluorescence of the excited photocatalyst could be efficiently quenched by the mixture of 1aa and base (Fig. ). Additionally, light on/off experiment as well as a measured quantum yield of 0.31 for the reaction led us to rule out the possible of radical chain mechanism (See SI).