Isostructural bis-1,2,3-thiaselenazolyl dimers

Area of Science:

• Materials Science
• Solid-State Chemistry
• Organic Electronics

Background:

• N-methylated bis-1,2,3-thiaselenazolylium salts are precursors to novel radical species.
• Understanding the solid-state properties of radical dimers is crucial for developing new electronic materials.

Purpose of the Study:

• To synthesize and characterize bis-1,2,3-thiaselenazolyl radicals and their corresponding dimers.
• To investigate the solid-state structure, electronic properties, and pressure-dependent conductivity of these radical dimers.

Main Methods:

• Electrochemical reduction of N-methylated bis-1,2,3-thiaselenazolylium salts to generate radicals.
• Single-crystal X-ray diffraction to determine the isomorphous crystal structures of the Se-Se bonded dimers.
• Electrical conductivity measurements as a function of applied pressure.

Main Results:

• The reduction yielded bis-1,2,3-thiaselenazolyl radicals (2a,b,c) which crystallized as centrosymmetric Se-Se sigma-bonded dimers.
• The crystal structures revealed interpenetrating pi-stack arrays with significant intermolecular Se-N' and Se-S' contacts.
• The dimers behaved as small band gap semiconductors with a room temperature conductivity of ~10(-6) S cm(-1), which dramatically increased under pressure (up to 10(1) S cm(-1) for [2a](2) at 5 GPa).

Conclusions:

• The Se-Se bonded bis-1,2,3-thiaselenazolyl dimers are diamagnetic in the solid state and exhibit semiconductor behavior.
• Pressure significantly enhances the conductivity of these materials, with compound [2a](2) showing superior compressibility and conductivity response.
• These findings highlight the potential of these radical dimers as pressure-sensitive organic semiconductors.