Ionic-Liquid-Based Synthesis of U₂₄ Uranyl Peroxide Cage Clusters with Encapsulated Hexanuclear Lanthanide...

Area of Science:

• Inorganic Chemistry
• Materials Science
• Crystal Engineering

Background:

• Uranyl peroxide cage clusters (UPCs) are typically synthesized in alkaline aqueous conditions.
• Lanthanide-containing UPCs are difficult to form due to precipitation of insoluble lanthanide compounds.
• Studtite, [(UO2)(O2)(H2O)2](H2O)2, is a known precursor for UPC synthesis.

Purpose of the Study:

• To develop a new method for synthesizing lanthanide-containing uranyl peroxide cage clusters (UPCs).
• To investigate the formation of UPCs using studtite dissolved in an ionic liquid.
• To characterize the structure and properties of novel lanthanide-containing UPCs.

Main Methods:

• Dissolution of studtite and lanthanide nitrates in the ionic liquid 1-ethyl-3-methylimidazolium diethyl phosphate (EMIm-DEP).
• Isolation and characterization of crystalline compounds using single crystal X-ray diffraction.
• Spectroscopic analysis (Raman, infrared) and electron microscopy (SEM-EDX).

Main Results:

• Six lanthanide-containing UPCs (Pr-Tb, excluding Pm) were successfully synthesized.
• The structures feature U24 cage clusters with sodalite topology, encapsulating hexanuclear lanthanide units ([Ln6O(OH)8]8+).
• Highly porous crystal structures were formed, with EMIm-DEP ions balancing charge within the pores.

Conclusions:

• The dissolution of studtite in an ionic liquid provides a viable route for synthesizing lanthanide-containing UPCs.
• This study reports the first formation of U24 cage clusters incorporating lanthanide cations.
• The developed method overcomes the limitations of traditional aqueous synthesis for these complex inorganic structures.