Infrared Spectroscopy of Matrix-Isolated Neutral and Ionized Anthracoronene in Argon

Area of Science:

• Spectroscopy
• Quantum Chemistry
• Materials Science

Background:

• Polycyclic Aromatic Hydrocarbons (PAHs) are crucial in astrochemistry and materials science.
• Understanding the spectral properties of large PAHs like anthracoronene (AnthCor) is key to identifying them in extraterrestrial environments and designing new materials.

Purpose of the Study:

• To experimentally measure and theoretically analyze the mid-IR and near-IR spectra of neutral and ionized anthracoronene.
• To compare the spectral features of AnthCor with its parent molecules, coronene and anthracene.
• To investigate the unique electronic transitions and anion formation of AnthCor.

Main Methods:

• Matrix-isolation infrared (IR) spectroscopy in argon.
• Density Functional Theory (DFT) calculations for theoretical spectral analysis.
• UV photolysis to induce ionization and anion formation.

Main Results:

• Experimental and DFT-calculated mid-IR spectra of AnthCor agreed within 0-10 cm^-1.
• Ionized AnthCor exhibited exceptionally intense cation and anion bands near 1330 and 1318 cm^-1.
• A novel, strong electronic transition was observed around 6175 cm^-1 in ionized AnthCor's NIR spectrum.
• AnthCor was identified as one of the few PAHs forming anions upon UV photolysis.

Conclusions:

• Anthracoronene possesses unique spectral characteristics, including intense IR bands and unusual electronic transitions, distinguishing it from smaller PAHs.
• The observed spectral features and anion formation provide valuable data for astronomical observations and potential applications in organic electronics.