Propeller-Shaped Blatter-Based Triradicals: Distortion-Free Triangular Spin System and Spin-State-Dependent...

Area of Science:

• Organic Chemistry
• Materials Science
• Quantum Chemistry

Background:

• Triptycene derivatives offer unique three-dimensional scaffolds for molecular design.
• Stable organic radicals are of interest for molecular electronics and spintronics.
• Controlling spin states in molecular systems is crucial for advanced functionalities.

Purpose of the Study:

• To synthesize and characterize novel triptycene-based C3v- and Cs-symmetric stable triradicals.
• To investigate the magnetic properties and spin-spin interactions of these triradicals.
• To explore the relationship between spin states and optical/electronic properties.

Main Methods:

• Synthesis of triptycene-based triradicals.
• Superconducting Quantum Interference Device (SQUID) magnetometry for magnetic characterization.
• Variable-temperature spectroscopic studies and quantum chemical calculations.

Main Results:

• The propeller-shaped triradicals exhibited an antiferromagnetic equilateral triangle spin system with small spin-spin interactions (J/kB ≈ -120 K and -106 K).
• A coexistence of doublet and quartet spin states (approx. 4/6 ratio) was observed at room temperature.
• Characteristic near-infrared absorption bands up to 1000 nm were observed, attributed to the doublet spin state.
• Spin-state-dependent charge transfer phenomena were identified: low-spin states underwent symmetry-breaking charge transfer, while high-spin states transitioned to a monoradical-like excited state.

Conclusions:

• The synthesized triptycene triradicals possess tunable magnetic properties and distinct spin-state-dependent optical behaviors.
• The spin-specific near-infrared absorption provides a method to differentiate between spin states.
• These findings open avenues for designing functional molecular materials based on controlled spin states and charge transfer.