Oligomers Intermediates in Between Two New Distinct Homonuclear Uranium(IV) DOTP Complexes*.

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Uranium Chemistry

Background:

• Uranium(IV) chemistry is crucial for nuclear fuel cycles and waste management.
• Macrocyclic ligands offer unique coordination environments for metal ions.
• Understanding uranium speciation in aqueous solutions is vital for environmental and safety assessments.

Purpose of the Study:

• To synthesize and characterize novel aqueous uranium(IV) complexes with the DOTP ligand.
• To investigate the structural diversity and chemical behavior of these complexes.
• To elucidate the interchange mechanism between different uranium(IV) species.

Main Methods:

• Synthesis of aqueous U(IV) complexes.
• X-ray crystallography for structural determination.
• UV-Vis absorption, NMR (1H, 31P), ATR-IR, and MALDI-TOFMS for characterization and interchange studies.

Main Results:

• Two distinct homonuclear U(IV)-DOTP complexes were identified: an "out-of-cage" [U(DOTPH6)2] and an "in-cage" [U(DOTPH4)].
• The "out-of-cage" complex features U(IV) octa-coordinated in a square anti-prism geometry (C4 symmetry).
• A one-way chemical interchange between these species was observed, leading to the formation of soluble oligomeric species with varied stoichiometries.

Conclusions:

• The study successfully synthesized and characterized two novel aqueous U(IV) complexes with the DOTP ligand.
• The findings reveal complex structural arrangements and dynamic chemical interchange between U(IV) species.
• The formation of oligomeric species highlights the complexity of uranium speciation in aqueous solutions.