Mapping structure-property relationships in a 6-oxo-verdazyl radical by variable pressure crystallography and density...

Area of Science:

• Solid-state chemistry
• Materials science
• Computational chemistry

Background:

• The 1,5-tolyl-3-phenyl-6-oxo-verdazyl radical (pTolOV) is a molecule of interest due to its radical nature.
• Understanding pressure-induced changes in crystalline organic materials is crucial for their technological applications.

Purpose of the Study:

• To investigate the structural, electronic, and magnetic responses of pTolOV to applied pressure in the crystalline state.
• To elucidate the pressure-dependent phase transitions and their impact on material properties.

Main Methods:

• High-pressure X-ray diffraction (XRD) techniques were employed to study structural changes.
• Periodic density functional theory (DFT) calculations were used to model electronic properties and magnetic interactions.

Main Results:

• A pressure-induced phase transition was observed between P2₁/n and C2/c space groups (2.30–2.73 GPa) with increased molecular symmetry.
• The band gap initially decreased slightly with pressure before sharply increasing in the C2/c phase, remaining in the 1.94–2.02 eV range.
• Weak antiferromagnetic exchange interactions were identified in antiparallel π-stacked chains.

Conclusions:

• The pTolOV radical undergoes a pressure-induced phase transition with significant structural and electronic property modifications.
• The material behaves as a wide-gap semiconductor across the studied pressure range.
• DFT calculations provide insights into the interplay between structure, electronic properties, and magnetic interactions under pressure.