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Li W, Wu M, Wang C, Huang J, Yang J, Xu M, Zhang F, Yang T, Zhao L. Unconventional pathway for the gas-phase formation of 14π-PAHs via self-reaction of the resonantly stabilized radical fulvenallenyl (C 7H 5˙). Chem Sci 2025; 16:7864-7875. [PMID: 40181816 PMCID: PMC11963888 DOI: 10.1039/d5sc00160a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2025] [Accepted: 03/06/2025] [Indexed: 04/05/2025] Open
Abstract
Resonantly stabilized free radicals (RSFRs) are contemplated to be the reactive intermediates in molecular mass-growth processes leading to polycyclic aromatic hydrocarbons (PAHs), which are prevalent in deep space and on Earth. The self-reaction routes of two RSFRs have been recognized as fundamental but more-efficient pathways to form fused benzenoid rings. The present experiment, which exploits a chemical microreactor in combination with an isomer-selective identification technique through fragment-free photoionization utilizing a tunable vacuum ultraviolet (VUV) light in tandem with the detection of the ionized molecules by a high-resolution reflection time-of-flight mass spectrometer (Re-TOF-MS), provides compelling evidence for the formation of phenanthrene and a minor amount of anthracene in the presence of fulvenallenyl (C7H5˙). Further theoretical calculations of the potential energy surfaces of C14H10 and C14H11 reveal that phenanthrene and anthracene can be efficiently produced via a hydrogen-assisted multi-step mechanism [C7H5˙ + C7H5˙ → i3, i3 = (3,4-di(cyclopenta-2,4-dien-1-ylidene)cyclobut-1-ene); i3 + H → phenanthrene + H/anthracene + H or i3 + H → i8 + H → phenanthrene + H/anthracene + H, i8 = (1-(cyclopenta-2,4-dien-1-ylidene)indene)] at low pressures, rather than through the one-step recombination-isomerization of fulvenallenyl radicals. This study provides a novel growth mechanism for tricyclic PAHs, especially in hydrogen-rich environments such as combustion and interstellar environments, which advances the knowledge of PAH propagation and even the formation mechanisms of carbonaceous nanoparticles in our universe.
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Affiliation(s)
- Wang Li
- National Synchrotron Radiation Laboratory, University of Science and Technology of China Hefei Anhui 230029 China
| | - Mengqi Wu
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei Anhui 230026 China
| | - Changyang Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China Hefei Anhui 230029 China
| | - Jiabin Huang
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei Anhui 230026 China
| | - Jiuzhong Yang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China Hefei Anhui 230029 China
| | - Minggao Xu
- National Synchrotron Radiation Laboratory, University of Science and Technology of China Hefei Anhui 230029 China
| | - Feng Zhang
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China Hefei Anhui 230026 China
- Hefei National Laboratory, University of Science and Technology of China Hefei Anhui 230088 China
| | - Tao Yang
- State Key Laboratory of Precision Spectroscopy, East China Normal University Shanghai 200062 China
- Xinjiang Astronomical Observatory, Chinese Academy of Sciences 150 Science 1-Street Urumqi Xinjiang 830011 China
- Collaborative Innovation Center of Extreme Optics, Shanxi University Taiyuan Shanxi 030006 China
| | - Long Zhao
- School of Nuclear Science and Technology, University of Science and Technology of China Hefei Anhui 230027 China
- Deep Space Exploration Laboratory, University of Science and Technology of China Hefei Anhui 230026 China
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Zhang YF, Li W, Wang CY, Huang C, Bian HT, Zhao L. Formation of C 5H 6 isomers: a combination of experimental and computational investigation. Phys Chem Chem Phys 2025; 27:4934-4943. [PMID: 39962987 DOI: 10.1039/d4cp03728f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2025]
Abstract
A propagation mechanism originating from 1,3-cyclopentadienyl, a prearomatic resonantly stabilized radical, makes a significant contribution to the growth of polycyclic aromatic hydrocarbons and soot. 1,3-Cyclopentadiene, as the simplest 5-membered carbon closed-shell molecule that could generate 1,3-cyclopentadienyl via photolysis and H-elimination, is attracting attention from astrochemistry and combustion chemistry communities. The reaction of propargyl (˙C3H3) with ethylene (C2H4) was investigated in a micro SiC reactor under low-pressure (<100 Torr) conditions coupled with tunable synchrotron radiation photoionization and molecular beam mass spectrometry techniques. Their potential energy surfaces were explored by ab initio electronic structure calculations. Subsequently, microscopic kinetics were demonstrated by RRKM/master equation theory in consideration of temperature- and pressure-dependent effects. The analysis of the photoionization efficiency (PIE) analysis at m/z = 66 has confirmed the formation of C5H6 molecules with a cyclic structure, i.e. 1,3-cyclopentadiene, as well as its linear isomer 3-penten-1-yne. Supported by ionization energies and Franck-Condon factors from theoretical predictions, this work proposes the possible formation of C5H6 molecules with two linear isomers 1,2,4-pentatriene and 4-penten-1-yne. Kinetics reveal the discrepancy of product selectivity under diverse temperatures and pressures. Notably, the generation of 1,2,4-pentatriene prevails at high temperatures corresponding to combustion environments, followed closely by 4-penten-1-yne and 3-penten-1-yne formations. Conversely, 1,3-cyclopentadiene shows a strong yield predominance in a vacuum environment within 300-600 K. This finding provides a potential pathway to aromatic hydrocarbon formation, especially in the planetary nebulae and circumstellar envelopes of carbon-rich stars.
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Affiliation(s)
- Yi-Fan Zhang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, China.
| | - Wang Li
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, China.
| | - Chang-Yang Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, China.
| | - Chen Huang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, China.
| | - Hui-Ting Bian
- Technical Support Center for Prevention and Control of Disastrous Accidents in Metal Smelting, University of Science and Technology Beijing, Beijing, 100083, China.
| | - Long Zhao
- School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui, 230027, China.
- Deep Space Exploration Laboratory, University of Science and Technology of China, Hefei, Anhui, 230026, China
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Yang Z, Medvedkov IA, Goettl SJ, Nikolayev AA, Mebel AM, Li X, Kaiser RI. Low-temperature gas-phase formation of cyclopentadiene and its role in the formation of aromatics in the interstellar medium. Proc Natl Acad Sci U S A 2024; 121:e2409933121. [PMID: 39661056 DOI: 10.1073/pnas.2409933121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Accepted: 11/02/2024] [Indexed: 12/12/2024] Open
Abstract
The cyclopentadiene (C5H6) molecule has emerged as a molecular building block of nonplanar polycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanostructures such as corannulene (C20H10), nanobowls (C40H10), and fullerenes (C60) in deep space. However, the underlying elementary gas-phase processes synthesizing cyclopentadiene from acyclic hydrocarbon precursors have remained elusive. Here, by merging crossed molecular beam experiments with rate coefficient calculations and comprehensive astrochemical modeling, we afford persuasive testimony on an unconventional low-temperature cyclization pathway to cyclopentadiene from acyclic precursors through the reaction of the simplest diatomic organic radical-methylidyne (CH)-with 1,3-butadiene (C4H6) representing main route to cyclopentadiene observed in TaurusMolecular Cloud. This facile route provides potential solution for the incorporation of the cyclopentadiene moiety in complex aromatic systems via bottom-up molecular mass growth processes and offers an entry point to the low-temperature chemistry in deep space leading eventually to nonplanar PAHs in our carbonaceous Universe.
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Affiliation(s)
- Zhenghai Yang
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, HI 96822
| | - Iakov A Medvedkov
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, HI 96822
| | - Shane J Goettl
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, HI 96822
| | - Anatoliy A Nikolayev
- Laboratory of Combustion Physics and Chemistry, Samara National Research University, Samara 443086, Russia
| | - Alexander M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199
| | - Xiaohu Li
- Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi, Xinjiang 830011, People's Republic of China
- Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Urumqi, Xinjiang 830011, People's Republic of China
- Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, HI 96822
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Goettl SJ, Yang Z, He C, Somani A, Portela-Gonzalez A, Sander W, Mebel AM, Kaiser RI. Exploring the chemical dynamics of phenanthrene (C 14H 10) formation via the bimolecular gas-phase reaction of the phenylethynyl radical (C 6H 5CC) with benzene (C 6H 6). Faraday Discuss 2024; 251:509-522. [PMID: 38766758 DOI: 10.1039/d3fd00159h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
The exploration of the fundamental formation mechanisms of polycyclic aromatic hydrocarbons (PAHs) is crucial for the understanding of molecular mass growth processes leading to two- and three-dimensional carbonaceous nanostructures (nanosheets, graphenes, nanotubes, buckyballs) in extraterrestrial environments (circumstellar envelopes, planetary nebulae, molecular clouds) and combustion systems. While key studies have been conducted exploiting traditional, high-temperature mechanisms such as the hydrogen abstraction-acetylene addition (HACA) and phenyl addition-dehydrocyclization (PAC) pathways, the complexity of extreme environments highlights the necessity of investigating chemically diverse mass growth reaction mechanisms leading to PAHs. Employing the crossed molecular beams technique coupled with electronic structure calculations, we report on the gas-phase synthesis of phenanthrene (C14H10)-a three-ring, 14π benzenoid PAH-via a phenylethynyl addition-cyclization-aromatization mechanism, featuring bimolecular reactions of the phenylethynyl radical (C6H5CC, X2A1) with benzene (C6H6) under single collision conditions. The dynamics involve a phenylethynyl radical addition to benzene without entrance barrier leading eventually to phenanthrene via indirect scattering dynamics through C14H11 intermediates. The barrierless nature of reaction allows rapid access to phenanthrene in low-temperature environments such as cold molecular clouds which can reach temperatures as low as 10 K. This mechanism constitutes a unique, low-temperature framework for the formation of PAHs as building blocks in molecular mass growth processes to carbonaceous nanostructures in extraterrestrial environments thus affording critical insight into the low-temperature hydrocarbon chemistry in our universe.
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Affiliation(s)
- Shane J Goettl
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA.
| | - Zhenghai Yang
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA.
| | - Chao He
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA.
| | - Ankit Somani
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany.
| | | | - Wolfram Sander
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany.
| | - Alexander M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA.
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA.
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Wang CY, Zhao L, Kaiser RI. Gas-Phase Preparation of the 14π Hückel Polycyclic Aromatic Anthracene and Phenanthrene Isomers (C 14H 10) via the Propargyl Addition-BenzAnnulation (PABA) Mechanism. Chemphyschem 2024; 25:e202400151. [PMID: 38635959 DOI: 10.1002/cphc.202400151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 04/11/2024] [Accepted: 04/12/2024] [Indexed: 04/20/2024]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) imply the missing link between resonantly stabilized free radicals and carbonaceous nanoparticles, commonly referred to as soot particles in combustion systems and interstellar grains in deep space. Whereas gas phase formation pathways to the simplest PAH - naphthalene (C10H8) - are beginning to emerge, reaction pathways leading to the synthesis of the 14π Hückel aromatic PAHs anthracene and phenanthrene (C14H10) are still incomplete. Here, by utilizing a chemical microreactor in conjunction with vacuum ultraviolet (VUV) photoionization (PI) of the products followed by detection of the ions in a reflectron time-of-flight mass spectrometer (ReTOF-MS), the reaction between the 1'- and 2'-methylnaphthyl radicals (C11H9⋅) with the propargyl radical (C3H3⋅) accesses anthracene (C14H10) and phenanthrene (C14H10) via the Propargyl Addition-BenzAnnulation (PABA) mechanism in conjunction with a hydrogen assisted isomerization. The preferential formation of the thermodynamically less stable anthracene isomer compared to phenanthrene suggests a kinetic, rather than a thermodynamics control of the reaction.
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Affiliation(s)
- Chang Yang Wang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230029, China
| | - Long Zhao
- School of Nuclear Science and Technology, Deep Space Exploration Laboratory, University of Science and Technology of China, Hefei, Anhui, 230026, China
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii, 96888, USA
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Biswas S, Paul D, Dias N, Lu W, Ahmed M, Pantoya ML, Kaiser RI. Efficient Oxidative Decomposition of Jet-Fuel exo-Tetrahydrodicyclopentadiene (JP-10) by Aluminum Nanoparticles in a Catalytic Microreactor: An Online Vacuum Ultraviolet Photoionization Study. J Phys Chem A 2024; 128:1665-1684. [PMID: 38383985 DOI: 10.1021/acs.jpca.3c08125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
The oxidation of gas-phase exo-tetrahydrodicyclopentadiene (JP-10, C10H16) over aluminum nanoparticles (AlNP) has been explored between a temperature range of 300 and 1250 K with a novel chemical microreactor. The results are compared with those obtained from chemical microreactor studies of helium-seeded JP-10 and of helium-oxygen-seeded JP-10 without AlNP to gauge the effects of molecular oxygen and AlNP, respectively. Vacuum ultraviolet (VUV) photoionization mass spectrometry reveals that oxidative decomposition of JP-10 in the presence of AlNP is lowered by 350 and 200 K with and without AlNP, respectively, in comparison with pyrolysis of the fuel. Overall, 63 nascent gas-phase products are identified through photoionization efficiency (PIE) curves; these can be categorized as oxygenated molecules and their radicals as well as closed-shell hydrocarbons along with hydrocarbon radicals. Quantitative branching ratios of the products reveal diminishing yields of oxidized species and enhanced branching ratios of hydrocarbon species with the increase in temperature. While in the low-temperature regime (300-1000 K), AlNP solely acts as an efficient heat transfer medium, in the higher-temperature regime (1000-1250 K), chemical reactivity is triggered, facilitating the primary decomposition of the parent JP-10 molecule. This enhanced reactivity of AlNP could plausibly be linked to the exposed reactive surface of the aluminum (Al) core generated upon the rupture of the alumina shell material above the melting point of the metal (Al).
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Affiliation(s)
- Souvick Biswas
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Dababrata Paul
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Nureshan Dias
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Wenchao Lu
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Musahid Ahmed
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Michelle L Pantoya
- Mechanical Engineering Department, Texas Tech University, Lubbock, Texas 79409, United States
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
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