Synthesis and Characterization of Non‐Aqueous [TcXM‐PW11O39]n– with M = O, N: Comparing TcV and TcVI in Metal Oxide Matrices

Technetium-99, a prevalent by-product of the nuclear fuel cycle, is a transition metal with 9 accessible oxidation states and a half-life of 2.1 x 10(5) years. Tc-99(VII) has been found in the environment surrounding National Lab sites and fuel reprocessing centers, and its separation and long-term storage is complicated by its extensive redox chemistry. In our prior work we have reported the synthesis and reduction of (TcO)-O-V to (TcO)-O-IV in alpha(1)- and alpha(2)-Wells-Dawson P2W17O6110- polyoxometalates and reported on the polyoxometalate features that promote reduction and stabilization. In this work we report on the oxidation state stabilization of (TcO)-O-V, (TcO)-O-VI and (TcN)-N-VI within the alpha-Keggin PW11O397- polyoxometalate. Both Density Functional Theory and experimental results show that Tc in TBA(4)[(TcN)-N-VI-PW11O39] can be reduced to Tc-V, but any subsequent electrons reduce the tungsten framework of the polyoxometalate. TBA(4)[(TcO)-O-V-PW11O39] however, can be theoretically reduced down to Tc-I before reduction of the polyoxometalate occurs.