Authors: Jacob W. Martin, Dingyu Hou, Angiras Menon, Laura Pascazio, Jethro Akroyd, Xiaoqing You, and Markus Kraft*

• The reactivity of aromatic soot precursors are studied.
• Covalent bond energies between aromatic soot precursors are calculated.
• Molecular structures combining physical interactions and covalent bonds are shown.

This paper presents a systematic study of the reactivity of polycyclic aromatic hydrocarbons (PAH), identifying crosslinks that permit the combination of physical π-stacking interactions and covalent bonding. Hybrid density functional theory was used to identify the location of reactive sites on PAHs using the average local ionization potential. The bond energies formed between these various reactive sites were then computed. σ-Radicals were found to be the most reactive, forming bonds with other radicals and some reactive closed shell edge types. Partially saturated rim-based pentagonal rings were found to form localized π-radicals with high reactivity. This site, in addition to resonantly stabilized π-radicals, was found to be capable of bonding and stacking, which is explored for a variety of larger species. Localized π-radicals on rim-based pentagonal rings, in particular, were found to form strongly bound stacked complexes, indicating a potentially important role in soot formation.

• This paper draws from preprint 234: Reactivity of polycyclic aromatic hydrocarbon radicals: implications for soot formation
• Access the article at the publisher: DOI: 10.1021/acs.jpcc.9b07558

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