Substrate-Affinitive P-Type Azapolycyclic Photosensitizer for Chemoselective Nitrilization Under Mild Conditions

Herein we report azapolycyclic quinoxalinoquinoxaline (QQ) photosensitizers featuring both tunable reducing ability and hydrogen-bonding assisted substrate affinity. The QQ-Ar photosensitizers are easily accessible on the gram scale and can be purified via vacuum sublimation, highlighting their potential for vapor-phase deposition in semiconductor applications. Their strong excited-state reduction potentials (E(PC^•+/PC^*) = -1.76 to -2.05 V vs SCE) arise from tunable ground-state oxidation potentials modulated by the aryl substituent. Despite the high reducing ability, the formation of honeycomb hydrogen-bonding network with carbonyl substates enables direct nitrilization of primary amides under mild conditions. A broad range of aryl, heteroaryl, olefinic, and alkyl amides, as well as pharmaceutical derivatives, were converted to nitriles with high functional group tolerance and scalability. Spectroscopic and computational studies support a mechanism involving oxidative quenching and selective hydrogen atom abstraction. This work establishes QQ photosensitizers as a practical and versatile platform for amide-to-nitrile conversions under mild conditions, with potential utility in both industrial and synthetic applications.