Breaking Bonds and Forming Nanographene Diradicals with Pressure

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Anthanthrone derivatives offer unique polycyclic aromatic hydrocarbon (PAH) scaffolds.
• Peripheral crowding in PAHs can induce non-planar geometries and novel electronic properties.

Purpose of the Study:

• To synthesize and characterize novel anthanthrone-based polycyclic scaffolds.
• To investigate the fluxional behavior and structural transitions of these compounds.
• To explore the formation of diradicaloid states and nanographene-like structures.

Main Methods:

• Synthesis of anthanthrone-based polycyclic compounds.
• Spectroscopic analysis (1H NMR, Raman spectroscopy).
• Quantum chemical calculations.
• Magnetic susceptibility measurements.
• Application of external pressure.

Main Results:

• Preparation of anthanthrone-based scaffolds with peripheral crowded quinodimethanes.
• Compounds exhibit a butterfly-shaped ground state that undergoes fluxional inversion to a planar structure.
• Inversion is facilitated by steric strain release and accessible via a biradicaloid transition state.
• Planarization occurs in solution at moderate temperatures and upon application of mild pressure in the solid state.
• Formation of a nanographene-like structure with kinetically trapped diradical centers.

Conclusions:

• Anthanthrone scaffolds can undergo significant structural transformations driven by strain and external stimuli.
• Mild pressure is a viable method to induce planarization and trap diradical states in the solid state.
• These findings open avenues for designing responsive materials with tunable electronic properties.