Strategy for Stimuli-Induced Spin Control Using a Liquescent Radical Cation

Area of Science:

• Materials Science
• Solid-State Chemistry
• Supramolecular Chemistry

Background:

• Phenothiazine radical cations are known for their rich redox and magnetic properties.
• Controlling solid-state spin states in molecular materials is a significant challenge in materials science.

Purpose of the Study:

• To investigate the effect of mechanical stress on the solid-state properties of a liquescent salt based on an N-pentylphenothiazine radical cation.
• To explore the mechanism behind stress-induced solid-state spin state transitions.

Main Methods:

• Synthesis of the N-pentylphenothiazine radical cation salt (1·NTf).
• Induction of crystal-crystal phase transition using pinpoint mechanostress.
• Characterization using electron spin resonance (ESR) and electronic spectroscopies.

Main Results:

• A unique crystal-crystal phase transition was observed, changing the material from a paramagnetic orange solid to a diamagnetic green solid.
• The transition was induced by brief, weak, and pinpoint mechanostress.
• Electron spin resonance and electronic spectroscopies confirmed the solid-state spin controllability.

Conclusions:

• Mechanostress can effectively control the spin state of the N-pentylphenothiazine radical cation in the solid state.
• The observed phenomenon is attributed to mechanostress-triggered sequential association of highly mobile radical species.
• This study presents a novel approach for solid-state spin control in molecular materials.