A high-spin diradical dianion and its bridged chemically switchable single-molecule magnet

Area of Science:

• Organic Chemistry
• Materials Science
• Quantum Physics

Background:

• Triplet diradicals are crucial for organic spintronics, magnets, and spin filters.
• Stable diradicals with large singlet-triplet energy gaps (ΔE_ST) are rare, especially exceeding room temperature thermal energy (0.59 kcal mol^-1 at 298 K).

Purpose of the Study:

• To synthesize and characterize novel triplet diradicals with substantial singlet-triplet energy gaps.
• To investigate the role of diradicals in single-molecule magnetism.

Main Methods:

• Synthesis of magnesium complex 1 containing the 2,7-di-tert-butyl-pyrene-4,5,9,10-tetraone (2,7-tBu₂-PTO) dianion.
• Characterization of the diradical dianion's properties, including its singlet-triplet energy gap.
• Synthesis of an iron analog 2 and its doubly reduced form 2K2 to study single-molecule magnetism.

Main Results:

• The magnesium complex 1 exhibited a triplet ground state diradical with a ΔE_ST of 0.94 kcal mol^-1 at 473 K, exceeding room temperature thermal energy.
• The iron analog 2 was the first single-molecule magnet bridged by a diradical dianion.
• Single-molecule magnetism was suppressed in the doubly reduced salt 2K2, emphasizing the diradical's role.

Conclusions:

• Stable triplet diradicals with large singlet-triplet energy gaps can be synthesized, advancing organic spintronics.
• Diradical dianions are critical components for designing single-molecule magnets.
• The study provides a rare example of diradicals with significant energy gaps, opening new avenues in molecular magnetism.