The photochemical generation of superoxide Rh(III) complexes

The photolysis products of the [Rh(NH3)(5)(NO2)](NO3)(2) complex in aqueous solutions were studied by electron paramagnetic resonance (EPR), UV-visible (UV-vis), and N-15 nuclear magnetic resonance (N-15 NMR) spectroscopies. Aqueous solutions of [Rh(NH3)(5)(NO2)](NO3)(2) became blue when exposed to UV irradiation under an oxygen-containing atmosphere while aqueous solutions of [Rh(NH3)(5)(NO2)](NO3)(2) with additives of NaNO2 turned orange under the same conditions. Photolysis of degassed [Rh(NH3)(5)(NO2)](NO3)(2) solutions did not lead to any change of their color. It was suggested that, as a result of the photolysis, the complex decomposed with the formation of a NO2 fragment and a fragment containing Rh(ii). In the presence of molecular oxygen in solution, a superoxide complex, [Rh(NH3)(5)O-2](2+), was formed, in which electron transfer from the metal ion to O-2 took place.