To monitor the light-driven formation of Rh I phenPer, solutions of Rh III phenPer (10 µM) in water:acetonitrile mixture (4:1, v:v) in the presence of the electron donor triethylamine (400 µM) were irradiated at 400 nm (14 mW cm -2 ) or 470 nm (45 mW cm -2 . While the absorption of phenPer is only minor affected by the LED illumination, new absorption features arise at 450 and 695 nm for Rh I phenPer. The UVvis spectra for phenPer were recorded to exclude the involvement of the Per unit of phenPer in the for Rh III phenPer obtained band at 695 nm (see Fig. ).