Technetium and Rhenium Auto-reduction, Polymerization and Lability towards Group VII Polyoxometalate Chemistry

Area of Science:

• Coordination Chemistry
• Inorganic Chemistry
• Radiochemistry

Background:

• Group VII elements, Technetium (Tc) and Rhenium (Re), are crucial for radiopharmaceuticals and nuclear materials management.
• Fundamental research explores polyoxometalates and metal-metal bonded complexes at this periodic table crossroads.

Purpose of the Study:

• To investigate the chemistry of polynuclear Rhenium (Re) and Technetium (Tc) compounds.
• To understand the autoreduction behavior of Re and Tc.
• To compare the stability and lability of Re- and Tc-containing polyoxometalates.

Main Methods:

• Single-crystal X-ray diffraction for structural characterization.
• Re-L1 X-ray absorption near-edge spectroscopy to confirm oxidation states.
• Small-angle X-ray scattering and 99Tc nuclear magnetic resonance spectroscopy for solution phase dynamics.
• Computational methods to analyze 99Tc chemical shifts and lability.

Main Results:

• Isolation and characterization of green, metastable (ReVI,oct)2(ReVII,tet)2(OH)2(O)12·H2O crystals, demonstrating Re autoreduction.
• Isolation and structural characterization of [Tc4O4(H2O)2(ReO4)14]2− (Tc4Re14) polyanion crystals containing Tc(V) and Re(VII).
• Established a qualitative lability order of oxo-linkages: Re-O-Re > Re-O-Tc > Tc-O-Tc.
• Demonstrated greater stability of reduced Tc compared to reduced Re.

Conclusions:

• Rhenium (Re) exhibits autoreduction, similar to Manganese (Mn) and Technetium (Tc).
• Rhenium (Re) is an imperfect surrogate for Technetium (Tc) based on reducibility and solution dynamics.
• Further exploration of Group VII polyoxometalate chemistry holds significant promise.