Rare-earth squarate frameworks with topology

Area of Science:

• Materials Science
• Coordination Chemistry
• Solid-State Chemistry

Background:

• Squarate ligands (C4O4^2-) are planar, 4-connected molecules with D4h symmetry.
• These ligands are known to form diverse network topologies through coordination with metal ions.
• Rare-earth ions offer unique electronic and coordination properties for framework construction.

Purpose of the Study:

• To explore the assembly of squarate ligands with rare-earth ions.
• To synthesize and characterize novel coordination frameworks.
• To investigate the functional properties, such as proton conductivity and luminescence, of the resulting materials.

Main Methods:

• Hydrothermal synthesis was employed to construct the coordination frameworks.
• Powder X-ray diffraction (PXRD) was used for structural characterization.
• Proton conductivity measurements were performed under varying humidity conditions.
• Luminescence spectroscopy was utilized to study the response to specific analytes.

Main Results:

• A series of (4, 8)-connected frameworks with the 'smallest' type topology were successfully synthesized.
• The terbium-based analogue demonstrated significant proton conductivity.
• This terbium compound exhibited selective luminescence responses to permanganate (MnO4-) and dichromate (Cr2O7^2-) ions.

Conclusions:

• The squarate ligand is effective in constructing complex (4, 8)-connected rare-earth frameworks.
• The terbium-based material displays promising proton conductivity and luminescence sensing capabilities.
• These findings highlight the potential of rare-earth squarate frameworks as multifunctional materials for sensing and energy applications.