A Molecular Playground for Spin-State Ice and Coupled Electron-Spin Dynamics

Area of Science:

• Molecular Magnetism
• Supramolecular Chemistry
• Materials Science

Background:

• Combining spin-crossover (SCO) and metal-to-metal electron transfer (MMET) in single molecular systems is challenging due to strong coupling and short-lived intermediates.
• Developing molecular materials with multiple, switchable magnetic states is crucial for advanced electronic applications.

Purpose of the Study:

• To design and synthesize novel {W6Co9} clusters capable of exhibiting both SCO and MMET phenomena.
• To investigate the coexistence of SCO, MMET, and photoinduced slow magnetic relaxation in these molecular systems.
• To explore the impact of ligand fields and supramolecular packing on distinct switching behaviors and cooperative spin-state transitions.

Main Methods:

• Synthesis of cyanide-bridged {W6Co9} clusters with varying ligands (L) and solvent molecules.
• Characterization of magnetic properties, including spin-crossover transitions and photoinduced effects.
• Analysis of supramolecular packing and elastic frustration to understand cooperative spin-state switching.

Main Results:

• Demonstrated unprecedented coexistence of reversible SCO, MMET, and photoinduced slow magnetic relaxation in the synthesized {W6Co9} clusters.
• Achieved distinct switching behaviors: one-step incomplete transitions in elastically frustrated triangular-packed systems (1 and 3) and a two-step complete transition in a nonfrustrated grid-like system (2).
• Observed 'spin-state-ice-like' behavior in frustrated systems, with triangular units adopting 2HS/1LS or 1HS/2LS configurations, a first for molecular clusters.

Conclusions:

• Established a new paradigm for designing multistable magnetic materials by coupling electronic and spin transitions.
• Highlighted the critical role of elastic frustration in controlling cooperative spin-state switching and achieving complex magnetic behaviors.
• These findings provide fundamental insights into the design principles for advanced molecular magnetic materials.