Nonprecious-metal-assisted photochemical hydrogen production from ortho-phenylenediamine

The combination of o-phenylenediamine (opda), which possesses two proton- and electron-pooling capability, with Fe(II) leads to the photochemical hydrogen-evolution reaction (HER) in THF at room temperature without addition of photosensitizers. From the THF solution, the tris(o-phenylenediamine) iron(II) complex, [Fe^II(opda)₃](ClO₄)₂ (1), was isolated as a photoactive species, while the deprotonated oxidized species was characterized by X-ray crystallographic analysis, electrospray ionization mass spectrometry, and UV-vis NIR spectra. Furthermore, the HER is photocatalyzed by hydroquinone, which serves as a H⁺/e^- donor. The present work demonstrates that the use of a metal-bound aromatic amine as a H⁺/e^- pooler opens an alternative strategy for designing nonprecious-metal-based molecular photochemical H₂ production/storage materials.