Technetium-99 (Tc-99) is a long-lived (2.13x105 years) radionuclide and exists in large quantities in waste tanks at national labs. Its nine accessible oxidation states make it highly reactive and complicate its redox chemistry. The development of long-term storage solutions for Tc require a fundamental understanding of its stability and redox chemistry in the relevant matrices. The [TcI(CO)3(H2O)3+] species may also be present; the chemistry of Tc(I) in environment and waste tank matrices has been sparsely studied. We extend study of [TcI(CO)3+] species using highly controlled metal oxides as models for minerals and solid-state materials. Keggin polyoxometalates (POMs) ([PW12O40]3-) are air stable metal oxide clusters, which can be tuned for size, charge, acidity, and redox potential. Experimental and theoretical research has shown that W substitution with one, two or three lower valent transition metals such as Vanadium(+5) or Niobium(+5) increases the surface Lewis basicity of the POM, thus rendering the surface more reactive to low valent metals and offering favorable tripodal coordination. Specifically, Nb and V substituted Keggin POMs, [PMxW12-xO40](3+x)-, where M = V, Nb and x=1,2, or 3 provide surfaces that vary in basicity, electronic environment and lability to probe the speciation and stability of Tc(I). Herein, we present an alternative approach to low pressure CO synthesis of the [TcI(CO)3+] core and provide an update on the surface stabilization of [TcI(CO)3+] on electron-rich metal oxide surfaces.

Recent advancements in using metal oxide matrices to investigate non-pertechnetate Tc species

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ACS Fall 2022

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