Solvent-Regulated Lattice Elasticity and Pressure-Induced Multi-Stimuli Spin-State Bistability in a Porous Hexagonal...

Area of Science:

• Materials Science
• Coordination Chemistry
• Supramolecular Chemistry

Background:

• Spin-state switching in molecular materials is crucial for advanced functionalities.
• Effective spin-state control often requires multiple external stimuli acting synergistically.
• Designing frameworks that respond to various stimuli is a key challenge in materials science.

Purpose of the Study:

• To report a new porous cyanide-bridged {4d-3d} heterobimetallic framework.
• To investigate the spin-state switching behavior induced by different external stimuli.
• To establish elastic-matrix squeezing as a unifying strategy for multi-stimuli bistability.

Main Methods:

• Single-crystal X-ray diffraction to determine the framework structure.
• Investigating thermally and light-induced spin-state switching.
• Studying spin-state switching under hydrostatic pressure.

Main Results:

• A flexible 3D hexagonal framework {[Mo(CN)8][Fe(v-im)4]2(BF4).2DMF.H2O}n was synthesized.
• Partial desolvation led to reversible thermally induced spin-state switching (T1/2 = 127 K) and LIESST effect (TLIESST = 60 K).
• The fully solvated framework showed pressure-induced spin-state switching, demonstrating multi-stimuli bistability.

Conclusions:

• The cooperative spin-state response arises from dynamic coupling between solvent molecules, counter-ions, and the flexible framework.
• Elastic-matrix squeezing provides a unifying strategy for achieving multi-stimuli bistability in molecular materials.
• This work highlights the integration of porosity, elasticity, and spin-crossover phenomena in adaptive molecular frameworks.