Combining electron transfer, spin crossover, and redox properties in metal-organic frameworks

Area of Science:

• Materials Science
• Coordination Chemistry
• Supramolecular Chemistry

Background:

• Hofmann coordination polymers (CPs) offer a platform for integrating spin transitions with ligand responsiveness.
• Metal-organic frameworks (MOFs) are explored for multifunctional applications.
• Spin crossover in Fe(II) complexes is a well-studied phenomenon.

Purpose of the Study:

• To develop novel coordination polymers coupling Fe(II) spin crossover with electron-responsive ligands.
• To investigate the thermochromic and electrochemical properties of these new materials.
• To explore their potential as multifunctional MOFs.

Main Methods:

• Synthesis of 2D planar coordination polymer networks.
• Temperature-dependent single-crystal X-ray diffraction.
• Magnetic measurements, Mössbauer, EPR, optical, and vibrational spectroscopies.
• Quantum chemical calculations.

Main Results:

• A novel coordination mode with infinitely π-stacked redox-active bipyridinium ligands was achieved.
• The materials displayed vivid thermochromism due to electron transfer and/or spin state changes.
• Quasi-reversible electrochemical reduction was observed on the spin-crossover complex in the solid state.

Conclusions:

• The developed coordination polymers exhibit coupled spin transition and redox activity.
• These materials demonstrate potential for creating stimuli-responsive and multifunctional MOFs.
• The findings open new avenues for designing advanced functional materials.