Microhydration of small protonated polyaromatic hydrocarbons: a first principles study

Area of Science:

• Computational Chemistry
• Physical Chemistry

Background:

• Protonated polycyclic aromatic hydrocarbons (H+PAHs) are significant in organic chemistry, astrochemistry, and atmospheric science.
• Understanding the microsolvation of H+PAHs by water is essential for predicting their behavior in different environments.

Purpose of the Study:

• To investigate the microsolvation of protonated benzene (BzH+), protonated coronene (CorH+), and protonated dodecabenzocoronene (DbcH+) using first-principles methodology.
• To analyze the structural, energetic, aromaticity, and spectral properties of H+PAH-water complexes.
• To elucidate the nature and strength of interactions between H+PAHs and water clusters.

Main Methods:

• First principles calculations were employed to model gas-phase complexes of H+PAHs with 1-3 water molecules.
• Structural, energetic, and aromaticity analyses were performed.
• Infrared (IR) and UV-Vis spectral features were calculated.
• Non-covalent interactions were quantified using non-covalent index and symmetry-adapted perturbation theory (SAPT0).

Main Results:

• The most stable configurations of mono-, di-, and tri-hydrated H+PAH complexes were identified.
• The strength of non-bonded interactions was correlated with electron density profiles.
• The influence of the extended π-aromatic system on solvation was investigated.
• Predictions for electronic transitions (S0 → S1 and S0 → T1) in aqueous solution were deduced.

Conclusions:

• The study provides a microscopic understanding of water-solvation effects on H+PAHs.
• Findings are relevant for diverse fields including organic chemistry, astrochemistry, atmospheric chemistry, combustion, and materials science.
• The research highlights the importance of non-bonded interactions in stabilizing these complexes.