Methyl Viologen Lead Iodide for Photocatalytic Reductive Coupling of Aromatic Carbonyls via Proton-Coupled Electron Transfer.

Organic-inorganic metal halides (OIMHs) have emerged as promising photocatalysts for organic transformations due to their excellent optoelectronic properties. However, their instability, particularly under protic conditions, has limited their broader applications. Here, we report that a facilely prepared methyl viologen lead iodide (MVPb2I6) powder can efficiently catalyze the visible-light-driven reductive coupling of aromatic aldehydes and ketones in protic solvents. Remarkably, MVPb2I6 retains its structural integrity after photoreduction, highlighting its robustness. These results suggest that incorporating quaternary pyridinium cations into the OIMHs can enhance their stability and expand their applicability in photocatalytic organic synthesis.