Cyclopenta-Fused Polyaromatic Hydrocarbon (CP-PAH) Radicals: Synthesis, Characterization, and Quantum Chemical...

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Polyaromatic hydrocarbons (PAHs) are crucial in materials science.
• Developing stable organic radicals is challenging due to their reactivity.
• Cyclopenta-fused PAHs offer unique electronic and structural properties.

Purpose of the Study:

• Synthesize novel, air- and moisture-stable cyclopenta-fused polyaromatic hydrocarbon (CP-PAH) radicals.
• Characterize the electronic and structural properties of these novel radicals.
• Investigate the stability and potential applications of CP-PAH radicals.

Main Methods:

• Multi-step synthesis involving Suzuki couplings and cyclizing S_EAr reactions.
• Electron Paramagnetic Resonance (EPR) and UV/Vis spectroscopy for characterization.
• Quantum chemical calculations for spectral simulation and property analysis.

Main Results:

• Successfully synthesized two stable CP-PAH radicals with complex fused ring systems.
• Mesityl substituents were key to achieving kinetic stability.
• EPR and UV/Vis spectroscopy confirmed radical character, with unpaired electrons localized in outer five-membered rings.
• Quantum chemical calculations provided insights into spin densities, aromaticity, and electronic structures, revealing antiaromatic character in central five-membered rings.

Conclusions:

• Novel stable CP-PAH radicals were synthesized and characterized.
• The study demonstrates a viable synthetic route to complex, stable organic radicals.
• These findings open avenues for exploring CP-PAH radicals in advanced materials and organic electronics.