Helical Co-based coordination polymer based on asymmetric ligands: synthesis, structure and properties

Area of Science:

• Coordination Chemistry
• Materials Science
• Crystallography

Background:

• Metal-organic frameworks (MOFs) and coordination polymers are crucial in materials science.
• Understanding self-assembly processes is key to designing novel functional materials.
• Cobalt(II) complexes offer diverse magnetic and electronic properties.

Purpose of the Study:

• To synthesize and characterize a new cobalt(II) coordination polymer using 2-methoxyterephthalic acid (H2mta) and 4-[4-(1H-imidazol-1-yl)phenyl]pyridine (ipp).
• To investigate the structural, electronic, and magnetic properties of the resulting complex, denoted as HU29.
• To explore the self-assembly behavior leading to complex network architectures.

Main Methods:

• Solvothermal synthesis of the coordination polymer.
• Structural characterization using single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis.
• Thermal stability analysis via thermogravimetric analysis (TGA).
• Electronic properties evaluated using UV-Vis absorption spectroscopy.
• Magnetic properties investigated through magnetic susceptibility measurements.

Main Results:

• The successful synthesis of poly[[{μ-4-[4-(1H-imidazol-1-yl)phenyl]pyridine}(μ-2-methoxyterephthalato)cobalt(II)] monohydrate], {[Co(mta)(ipp)]·H2O}n (HU29).
• Single-crystal X-ray diffraction revealed a 3D framework constructed from four distinct helical chains, exhibiting a fivefold interpenetrating structure.
• Topological analysis simplified the framework to a four-connected dia net.
• UV-Vis spectroscopy indicated a band gap of 2.72 eV, suggesting semiconductor behavior.
• Magnetic studies confirmed antiferromagnetic interactions within the complex.

Conclusions:

• The self-assembly reaction yields a complex, interpenetrating 3D coordination polymer with potential semiconductor applications.
• The structural complexity arises from the interplay of ligand geometry and metal ion coordination.
• The observed magnetic behavior provides insights into the electronic interactions within the cobalt centers.