Snapshots of Ce₇₀ Toroid Assembly from Solids and Solution

Area of Science:

• Inorganic Chemistry
• Materials Science
• Crystallography

Background:

• Crystallization at solid-liquid interfaces is difficult to observe and control at the molecular level.
• The Ce70-torroid cluster, [Ce70(OH)36(O)64(SO4)60(H2O)10]4-, is part of an emerging MIV70-material family (M = Zr, U, Ce).

Purpose of the Study:

• To elucidate the assembly mechanisms of the Ce70-torroid cluster.
• To understand the formation of fragments and their building units.
• To explore the potential applications of this emerging material family.

Main Methods:

• X-ray scattering (small-angle and total scattering) of solutions and solids.
• Single-crystal X-ray diffraction to identify Ce70 fragments.
• Observation of rapid room-temperature assemblies induced by Li+ and NH4+.

Main Results:

• Assembly mechanisms were elucidated through X-ray scattering and diffraction.
• Identified templated growth (Ce5) and modular assembly from hexamer units (Ce6) leading to larger clusters (Ce13, Ce62).
• Ce62 forms interlocking arcs via hydrogen bonding with NH4+, a novel inorganic structural motif.

Conclusions:

• The Ce70-torroid and its fragments exhibit modular assembly from smaller building units.
• The rapid assembly of Ce62 with ammonium cations and the ion-exchange/redox properties of these materials suggest potential in environmental and energy applications.