Photochemical Activation of an Azido Manganese-Monosubstituted Keggin Polyoxometalate: On the Road to a Mn(V)−Nitrido Derivative

The manganese(V)−nitrido polyoxometalate derivative [PW₁₁O₃₉{Mn^VN}]⁵⁻ has been synthesized by photochemical activation of the parent manganese(III)−azido derivative [PW₁₁O₃₉Mn^IIIN₃]⁵⁻. It was characterized by mass spectrometry, ³¹P NMR, UV−vis, and IR spectroscopies. An electrochemistry study indicated that only the Mn(V) state was stable. The photoactivation of the manganese(III)−azido derivative proceeds through two competitive routes, yielding to the targeted product of photooxidation {Mn^VN} or the undesirable product of photoreduction {Mn^IIL} (L = H₂O, N₃), depending on the photolysis conditions. A simplified photolysis mechanism involving two different excited states was proposed to account for the temperature and wavelength dependence.