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

The manganese(V)−nitrido polyoxometalate derivative [PW<sub>11</sub>O<sub>39</sub>{Mn<sup>V</sup>N}]<sup>5−</sup> has been synthesized by photochemical activation of the parent manganese(III)−azido derivative [PW<sub>11</sub>O<sub>39</sub>Mn<sup>III</sup>N<sub>3</sub>]<sup>5−</sup>. It was characterized by mass spectrometry, <sup>31</sup>P 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<sup>V</sup>N} or the undesirable product of photoreduction {Mn<sup>II</sup>L} (L = H<sub>2</sub>O, N<sub>3</sub>), depending on the photolysis conditions. A simplified photolysis mechanism involving two different excited states was proposed to account for the temperature and wavelength dependence.