Glutarimidedioxime complexation: extraction of uranium vs. interference of vanadium and molybdenum in seawater

Abstract

The cyclic imide dioxime ligand, glutarimidedioxime (H₃A), has emerged as a paradigm-shifting archetype in coordination and separation chemistry. Its prominence is driven by the formidable challenge of extracting ultra-trace uranium from seawater, a critical endeavor for sustainable nuclear energy. This review provides a comprehensive and critical synthesis of research that positions H₃A as the definitive active motif in advanced amidoxime-based sorbents. We first delineate its structural elucidation, optimal synthesis, and distinctive acid–base properties. A higher temperature (80–90 °C) promotes intramolecular cyclization of two adjacent nitrile groups and favors the synthesis of H₃A, while avoiding excess hydroxylamine to prevent the formation of glutarimidoxioxime. The core analysis presents a comparative examination of its coordination chemistry, governed by a hierarchy of ionic potentials. H₃A contains a conjugated system that forms very stable complexes with the uranyl ion. In the complex, H₃A coordinates with the uranyl ion through a tridentate chelation pocket. This strong coordination enables it to compete with carbonate for the uranyl ion even at ultra-low concentrations. A central focus is the ligand's exceptional ability to displace oxo ligands from vanadate, forming an ultra-stable, rare non-oxido V(V) complex [V(A)₂]⁻, which defines the severe vanadium interference problem. Furthermore, we critically examine the previously overlooked but critical interaction with molybdenum, which catalyzes the hydrolytic degradation of the H₃A motif and poses a fundamental threat to long-term sorbent viability. By integrating molecular-scale insights with macroscopic application performance, this review clarifies the intricate structure–property relationships responsible for both the promise and limitations of H₃A-based technology. Finally, we chart a course for future research, emphasizing ligand design strategies to decouple uranyl from vanadium affinity and to mitigate degradation pathways, thereby guiding the development of next-generation functional materials for resource recovery and separation science.