Aryl radical addition–dehydrocyclization drives rapid polycyclic aromatic hydrocarbon growth
Abstract
Polycyclic aromatic hydrocarbons are ubiquitous in space, yet astrochemical models fail to reproduce their observed abundances because known growth mechanisms are far too slow. Here, we report a plausible pathway for rapid polycyclic aromatic hydrocarbon mass growth mediated by multi-ring aryl radicals via the aryl addition–dehydrocyclization mechanism. High-temperature reactions of 1- and 2-naphthyl radicals with biphenyl and naphthalene serve as proof-of-concept, demonstrating the gas-phase formation of five-ring polycyclic aromatic hydrocarbons including benzo[b]triphenylene, benzo[4]helicene, benzo[k]fluoranthene, benzo[j]fluoranthene, and perylene through [3 + 2] zig-zag edge and [4 + 2] carbon bay closures. Products are identified isomer-selectively using tunable vacuum-ultraviolet photoionization coupled with i²PEPICO spectroscopy. Initiated by a single collision, the aryl addition–dehydrocyclization mechanism forms multiple carbon–carbon bonds, possibly accelerating polycyclic aromatic hydrocarbon growth compared with sequential pathways such as hydrogen abstraction–acetylene addition. This pathway provides a route from small aromatics to extended two- and three-dimensional carbon nanostructures, reshaping our understanding of aromatic carbon evolution in high-temperature astrophysical environments, from circumstellar envelopes to planetary nebulae, offering insights into the formation of complex carbonaceous molecules in space. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in space, yet astrochemical models fail to reproduce their observed abundances because known growth mechanisms are far too slow. Here, the authors report a plausible pathway for rapid PAH mass growth mediated by multi-ring aryl radicals via the aryl addition–dehydrocyclization mechanism.
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BibTeX
@article{goettl2026aryl,
title = {{Aryl radical addition–dehydrocyclization drives rapid polycyclic aromatic hydrocarbon growth}},
author = {Shane Goettl and Bing-Jian Sun and Andrew Turner and Myriam Drissi and Gustavo Garcia and Laurent Nahon and Komal Kadam and Agnes Chang and Ralf Kaiser},
journal = {Nature Communications},
year = {2026},
month = aug,
doi = {10.1038/s41467-026-76371-0},
url = {https://hal.science/hal-05773965v1},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Aryl radical addition–dehydrocyclization drives rapid polycyclic aromatic hydrocarbon growth
AU - Shane Goettl
AU - Bing-Jian Sun
AU - Andrew Turner
AU - Myriam Drissi
AU - Gustavo Garcia
AU - Laurent Nahon
AU - Komal Kadam
AU - Agnes Chang
AU - Ralf Kaiser
PY - 2026
DA - 2026/08/05
JO - Nature Communications
DO - 10.1038/s41467-026-76371-0
UR - https://hal.science/hal-05773965v1
AB - Polycyclic aromatic hydrocarbons are ubiquitous in space, yet astrochemical models fail to reproduce their observed abundances because known growth mechanisms are far too slow. Here, we report a plausible pathway for rapid polycyclic aromatic hydrocarbon mass growth mediated by multi-ring aryl radicals via the aryl addition–dehydrocyclization mechanism. High-temperature reactions of 1- and 2-naphthyl radicals with biphenyl and naphthalene serve as proof-of-concept, demonstrating the gas-phase formation of five-ring polycyclic aromatic hydrocarbons including benzo[b]triphenylene, benzo[4]helicene, benzo[k]fluoranthene, benzo[j]fluoranthene, and perylene through [3 + 2] zig-zag edge and [4 + 2] carbon bay closures. Products are identified isomer-selectively using tunable vacuum-ultraviolet photoionization coupled with i²PEPICO spectroscopy. Initiated by a single collision, the aryl addition–dehydrocyclization mechanism forms multiple carbon–carbon bonds, possibly accelerating polycyclic aromatic hydrocarbon growth compared with sequential pathways such as hydrogen abstraction–acetylene addition. This pathway provides a route from small aromatics to extended two- and three-dimensional carbon nanostructures, reshaping our understanding of aromatic carbon evolution in high-temperature astrophysical environments, from circumstellar envelopes to planetary nebulae, offering insights into the formation of complex carbonaceous molecules in space. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in space, yet astrochemical models fail to reproduce their observed abundances because known growth mechanisms are far too slow. Here, the authors report a plausible pathway for rapid PAH mass growth mediated by multi-ring aryl radicals via the aryl addition–dehydrocyclization mechanism.
SN - 2041-1723
SN - 2041-1723
ER -