Ligand-controlled mixed-valence copper rectangular grid-type coordination polymers based on pyridylterpyridine

Area of Science:

• Coordination Chemistry
• Materials Science
• Crystallography

Background:

• Mixed-valence copper compounds are of interest due to their unique electronic and magnetic properties.
• Terpyridine ligands offer versatile coordination possibilities for constructing complex metal-organic frameworks.

Purpose of the Study:

• To synthesize and characterize novel mixed-valence Cu(I)Cu(II) compounds.
• To investigate the structural diversity and dimensionality of these compounds based on ligand and counterion choice.
• To explore the influence of linker size on the formation of polymeric structures.

Main Methods:

• Hydrothermal and ambient synthesis of six mixed-valence copper compounds.
• Single-crystal X-ray diffraction for crystal structure determination.
• Temperature-dependent magnetic susceptibility studies.

Main Results:

• Successful synthesis of six mixed-valence Cu(I)Cu(II) compounds utilizing terpyridine ligands (L1 and L2).
• Formation of 1-dimensional and 2-dimensional polymers with rectangular grid-type building blocks (M(4)L(4) or M(6)L(6)).
• Demonstration of fine-tuning the size of M(4)L(4) units by varying halide/thiocyanate linker size.
• Structural differences observed in compound 6 due to ligand L2's uncoordinated pyridine moiety.

Conclusions:

• The choice of ligand, copper salt, and reaction conditions (hydrothermal vs. ambient) dictates the final structure and dimensionality of the mixed-valence copper compounds.
• The terpyridine ligands and halide/thiocyanate linkers play crucial roles in forming extended polymeric networks.
• Magnetic susceptibility studies confirm the presence of mixed-valence electronic structures in selected compounds.