Gas-Phase Synthesis of Coronene through Stepwise Directed Ring Annulation

Area of Science:

• Astrochemistry
• Physical Chemistry
• Materials Science

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are crucial in combustion and astrophysical environments.
• Coronene (C24H12) is a representative peri-fused PAH with significant chemical relevance.
• Understanding PAH formation pathways is essential for complex chemical systems.

Purpose of the Study:

• To provide the first evidence of a gas-phase reaction network for coronene synthesis.
• To elucidate the bottom-up preparation mechanism of coronene from smaller precursors.
• To explore molecular mass growth processes leading to two-dimensional carbonaceous nanostructures.

Main Methods:

• Combined molecular beam experiments and electronic structure calculations.
• Isomer-selective identification using photoionization techniques.
• Analysis of photoionization efficiency curves and threshold photoelectron spectra.

Main Results:

• Detailed the complex network of elementary gas-phase reactions leading to coronene.
• Identified benzo[e]pyrene and benzo[ghi]perylene as key intermediates in coronene formation.
• Observed aryl radical-mediated ring annulations involving various aromatic intermediates.

Conclusions:

• Established a comprehensive understanding of coronene's gas-phase synthesis.
• Highlighted the chemical diversity in molecular mass growth to PAHs.
• Demonstrated a versatile concept for forming carbonaceous nanostructures via radical intermediates.