Switchable Spin-Crossover Hofmann-Type 3D Coordination Polymers Based on Tri- and Tetratopic Ligands

Area of Science:

• Materials Science
• Chemistry
• Crystallography

Background:

• Hofmann-type coordination polymers featuring iron(II) spin-crossover (SCO) are well-established responsive materials.
• Traditional Hofmann-type architectures primarily utilize monotopic and linear ditopic pyridine-like ligands.

Purpose of the Study:

• To explore novel Hofmann-type architectures with SCO properties by employing bridging ligands with higher connectivity.
• To synthesize and characterize new coordination polymers using tritopic and tetratopic ligands.

Main Methods:

• Synthesis of novel coordination polymers using 1,3,5-tris(pyridin-4-ylethynyl)benzene (LN3) and 1,2,4,5-tetrakis(pyridin-4-ylethynyl)benzene (LN4) ligands.
• Structural characterization of the resulting Hofmann clathrates, including guest molecules like nitrobenzene, benzonitrile, and o-dichlorobenzene.
• Investigation of spin-crossover phenomena induced by thermal and light stimuli.

Main Results:

• Successful synthesis and structural determination of {FeII(LN3)[MI(CN)2]2}·(Guest) (MI = Ag, Au) and {FeII(LN4)[Ag2(CN)3][Ag(CN)2]}·H2O.
• Demonstration of thermo- and photoinduced spin-crossover (SCO) behaviors in these newly synthesized Hofmann clathrates.
• Expansion of ligand design strategies for creating advanced SCO materials.

Conclusions:

• The use of higher connectivity ligands (LN3 and LN4) enables the construction of novel Hofmann-type coordination polymers.
• These new materials exhibit promising spin-crossover properties, responsive to both temperature and light.
• This research broadens the design principles for developing advanced functional coordination polymers.