Allosteric Spin Crossover Induced by Ligand-Based Molecular Alloying

Area of Science:

• Coordination Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Spin crossover (SCO) phenomenon offers molecular-level multistability.
• Dilution into non-active hosts was crucial for understanding SCO cooperativity in solids.

Purpose of the Study:

• To develop a molecular alloying strategy using SCO-active components with distinct characteristic temperatures.
• To investigate the impact of composition on SCO behavior in novel molecular alloys.

Main Methods:

• Synthesis of [Fe(Mebpp)2-2x(Me2bpp)2x](ClO4)2 molecular alloys.
• Characterization using single-crystal X-ray diffraction (SCXRD).
• Analysis via magnetometry and differential scanning calorimetry (DSC).

Main Results:

• Alloying SCO-active components with different transition temperatures was achieved.
• Intermolecular interactions significantly influence SCO cooperativity.
• All components exhibited a one-step spin conversion at intermediate temperatures, demonstrating an allosteric SCO process.
• SCO temperature was tunable over a 42 K range.

Conclusions:

• The molecular alloying approach enables the creation of materials with tunable spin crossover properties.
• An unprecedented allosteric SCO mechanism was unveiled in these molecular alloys.
• This strategy offers a new pathway for designing advanced functional molecular materials.