1
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Wang J, Nikolayev AA, Marks JH, Turner AM, Chandra S, Kleimeier NF, Young LA, Mebel AM, Kaiser RI. Interstellar Formation of Nitrogen Heteroaromatics [Indole, C 8H 7N; Pyrrole, C 4H 5N; Aniline, C 6H 5NH 2]: Key Precursors to Amino Acids and Nucleobases. J Am Chem Soc 2024. [PMID: 39370877 DOI: 10.1021/jacs.4c09449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/08/2024]
Abstract
Nitrogen-substituted polycyclic aromatic hydrocarbons (NPAHs) are not only fundamental building blocks in the prebiotic synthesis of vital biomolecules such as amino acids and nucleobases of DNA and RNA but also a potential source of the prominent unidentified 6.2 μm interstellar absorption band. Although NPAHs have been detected in meteorites and are believed to be ubiquitous in the universe, their formation mechanisms in deep space have remained largely elusive. Here, we report the first bottom-up formation pathways to the simplest prototype of NPAHs, indole (C8H7N), along with its building blocks pyrrole (C4H5N) and aniline (C6H5NH2) in low-temperature model interstellar ices composed of acetylene (C2H2) and ammonia (NH3). Utilizing the isomer-selective techniques of resonance-enhanced multiphoton ionization and tunable vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry, indole, pyrrole, and aniline were identified in the gas phase, suggesting that they are promising candidates for future astronomical searches in star-forming regions. Our laboratory experiments utilizing infrared spectroscopy and mass spectrometry in tandem with electronic structure calculations reveal critical insights into the reaction pathways toward NPAHs and their precursors, thus advancing our fundamental understanding of the interstellar formation of aromatic proteinogenic amino acids and nucleobases, key classes of molecules central to the Origins of Life.
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Affiliation(s)
- Jia Wang
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | | | - Joshua H Marks
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Andrew M Turner
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Sankhabrata Chandra
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - N Fabian Kleimeier
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Leslie A Young
- Department of Space Studies, Southwest Research Institute, Boulder, Colorado 80302, United States
| | - Alexander M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Ralf I Kaiser
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
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2
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Johansen S, Park H, Wang LP, Crabtree KN. Reactant Discovery with an Ab Initio Nanoreactor: Exploration of Astrophysical N-Heterocycle Precursors and Formation Pathways. ACS EARTH & SPACE CHEMISTRY 2024; 8:1771-1783. [PMID: 39318708 PMCID: PMC11418024 DOI: 10.1021/acsearthspacechem.4c00120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2024] [Revised: 07/09/2024] [Accepted: 07/30/2024] [Indexed: 09/26/2024]
Abstract
The incorporation of nitrogen atoms into cyclic compounds is essential for terrestrial life; nitrogen-containing (N-)heterocycles make up DNA and RNA nucleobases, several amino acids, B vitamins, porphyrins, and other components of biomolecules. The discovery of these molecules on meteorites with non-terrestrial isotopic abundances supports the hypothesis of exogenous delivery of prebiotic material to early Earth; however, there has been no detection of these species in interstellar environments, indicating that there is a need for greater knowledge of their astrochemical formation and destruction pathways. Here, we present results of simulations of gas-phase pyrrole and pyridine formation from an ab initio nanoreactor, a first-principles molecular dynamics simulation method that accelerates reaction discovery by applying non-equilibrium forces that are agnostic to individual reaction coordinates. Using the nanoreactor in a retrosynthetic mode, starting with the N-heterocycle of interest and a radical leaving group, then considering the discovered reaction pathways in reverse, a rich landscape of N-heterocycle-forming reactivity can be found. Several of these reaction pathways, when mapped to their corresponding minimum energy paths, correspond to novel barrierless formation pathways for pyridine and pyrrole, starting from both detected and hypothesized astrochemical precursors. This study demonstrates how first-principles reaction discovery can build mechanistic knowledge in astrochemical environments as well as in early Earth models such as Titan's atmosphere where N-heterocycles have been tentatively detected.
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Affiliation(s)
| | | | - Lee-Ping Wang
- Department of Chemistry, University of California, Davis, Davis, California 95616, United States
| | - Kyle N. Crabtree
- Department of Chemistry, University of California, Davis, Davis, California 95616, United States
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3
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Chen X, Li Y, Xie M, Hu Y. Growth mechanism of aromatic prebiotic molecules: insights from different processes of ion-molecule reactions in benzonitrile-ammonia and benzonitrile-methylamine clusters. Phys Chem Chem Phys 2024; 26:21548-21557. [PMID: 39082110 DOI: 10.1039/d4cp01603c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2024]
Abstract
Benzonitrile (BN, C6H5CN) has been detected in the cold molecular cloud Taurus molecular cloud-1 (TMC-1) in 2018, which is suggested to be a precursor in the formation of more complex nitrogen-containing aromatic interstellar compounds. In this study, we utilized mass-selected infrared (IR) photodissociation spectroscopy and quantum chemical calculations to investigate the structures and gaseous ion-molecule reactions of benzonitrile-ammonia (BN-NH3) and benzonitrile-methylamine (BN-MA) clusters. The spectral observations indicate that the cyclic hydrogen bonding structure predominates in both neutral clusters. After VUV (118 nm) single-photon ionization, a new C-N covalent bond formed between BN and NH3 in the (BN-NH3)+ cluster. However, proton sharing constitutes the primary structure of the (BN-MA)+ cluster. The two nitrogen-containing interstellar molecules react with BN to yield distinct products due to difference in charge distribution and molecular polarity in the ionized clusters. The reactions of BN with other molecules contribute to our understanding of the growth mechanisms of complex interstellar molecules.
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Affiliation(s)
- Xutao Chen
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
| | - Yujian Li
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
| | - Min Xie
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
| | - Yongjun Hu
- MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, Guangzhou Key Laboratory of Spectral Analysis and Functional Probes, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
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4
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Karaev E, Gerlach M, Theil K, Garcia GA, Alcaraz C, Loison JC, Fischer I. Photoelectron spectrum of the pyridyl radical. Phys Chem Chem Phys 2024; 26:17042-17047. [PMID: 38836386 DOI: 10.1039/d4cp00688g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
We report the photoelectron spectrum of the pyridyl radical (C5H4N), a species of interest in astrochemistry and combustion. The radicals were produced via hydrogen abstraction in a fluorine discharge and ionized with synchrotron radiation. Mass-selected slow photoelectron spectra of the products were obtained from photoelectron-photoion coincidence spectra. A Franck-Condon simulation based on computed geometries and vibrational frequencies identified contributions of the o- and p-pyridyl radicals. For the o-isomer an adiabatic ionisation energy of 7.70 eV was obtained, in excellent agreement with a computed value of 7.72 eV. The spectrum of o-pyridyl is characterized by a long progression in an in-plane bending mode and the N-C stretch that contains the radical site.
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Affiliation(s)
- Emil Karaev
- University of Würzburg, Institute of Physical and Theoretical Chemistry, Am Hubland, 97074 Würzburg, Germany.
| | - Marius Gerlach
- University of Würzburg, Institute of Physical and Theoretical Chemistry, Am Hubland, 97074 Würzburg, Germany.
| | - Katharina Theil
- University of Würzburg, Institute of Physical and Theoretical Chemistry, Am Hubland, 97074 Würzburg, Germany.
| | - Gustavo A Garcia
- Synchrotron Soleil, L'Orme des Merisiers, St Aubin, B.P. 48, F-91192 Gif sur Yvette, France
| | - Christian Alcaraz
- Universite Paris-Saclay, CNRS, Institut de Chimie Physique, UMR8000, 91405 Orsay, France
| | | | - Ingo Fischer
- University of Würzburg, Institute of Physical and Theoretical Chemistry, Am Hubland, 97074 Würzburg, Germany.
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5
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Balucani N, Caracciolo A, Vanuzzo G, Skouteris D, Rosi M, Pacifici L, Casavecchia P, Hickson KM, Loison JC, Dobrijevic M. An experimental and theoretical investigation of the N( 2D) + C 6H 6 (benzene) reaction with implications for the photochemical models of Titan. Faraday Discuss 2023; 245:327-351. [PMID: 37293920 DOI: 10.1039/d3fd00057e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report on a combined experimental and theoretical investigation of the N(2D) + C6H6 (benzene) reaction, which is of relevance in the aromatic chemistry of the atmosphere of Titan. Experimentally, the reaction was studied (i) under single-collision conditions by the crossed molecular beams (CMB) scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy (Ec) of 31.8 kJ mol-1 to determine the primary products, their branching fractions (BFs), and the reaction micromechanism, and (ii) in a continuous supersonic flow reactor to determine the rate constant as a function of temperature from 50 K to 296 K. Theoretically, electronic structure calculations of the doublet C6H6N potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction mechanism. The reaction is found to proceed via barrierless addition of N(2D) to the aromatic ring of C6H6, followed by formation of several cyclic (five-, six-, and seven-membered ring) and linear isomeric C6H6N intermediates that can undergo unimolecular decomposition to bimolecular products. Statistical estimates of product BFs on the theoretical PES were carried out under the conditions of the CMB experiments and at the temperatures relevant for Titan's atmosphere. In all conditions the ring-contraction channel leading to C5H5 (cyclopentadienyl) + HCN is dominant, while minor contributions come from the channels leading to o-C6H5N (o-N-cycloheptatriene radical) + H, C4H4N (pyrrolyl) + C2H2 (acetylene), C5H5CN (cyano-cyclopentadiene) + H, and p-C6H5N + H. Rate constants (which are close to the gas kinetic limit at all temperatures, with the recommended value of 2.19 ± 0.30 × 10-10 cm3 s-1 over the 50-296 K range) and BFs have been used in a photochemical model of Titan's atmosphere to simulate the effect of the title reaction on the species abundances as a function of the altitude.
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Affiliation(s)
- Nadia Balucani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | - Adriana Caracciolo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | - Gianmarco Vanuzzo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | | | - Marzio Rosi
- Dipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Perugia, 06100, Perugia, Italy
| | - Leonardo Pacifici
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | - Piergiorgio Casavecchia
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | - Kevin M Hickson
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33400 Talence, France
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6
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Barik S, Behera NR, Dutta S, Kushawaha RK, Sajeev Y, Ramabhadran RO, Aravind G. Molecular growth of PANH via intermolecular Coulombic decay. SCIENCE ADVANCES 2023; 9:eadi0230. [PMID: 37494436 PMCID: PMC10371028 DOI: 10.1126/sciadv.adi0230] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 06/22/2023] [Indexed: 07/28/2023]
Abstract
Nitrogen-bearing polycyclic aromatic hydrocarbons (PANHs) are ubiquitous in space. They are considered precursors to advanced biomolecules identified in meteorites. However, their chemical evolution into biomolecules in photodestructive astrophysical mediums remains a paradox. Here, we show that light can efficiently initiate the molecular mass growth of PANHs. Ultraviolet-photoexcited quinoline monomers, the smallest PANH, were observed to associate and intermolecular Coulombic decay between the associating monomers formed the cations of quinoline-dimer. Molecular rearrangements in the dimer cation lead to a dominant formation of cations heavier than quinoline. The enrichment of these heavier cations over all the other cations reveals the efficiency of this route for the mass growth of PANHs in space. This mechanism also leads to a highly reactive unsaturated PANH-ring via CH loss, a hitherto unknown channel in any photon-driven process. The occurrence of this efficient pathway toward complex molecules points to a rich chemistry in dense interstellar clouds.
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Affiliation(s)
- Saroj Barik
- Department of Physics, Indian Institute of Technology Madras, Chennai, India
| | - Nihar Ranjan Behera
- Department of Physics, Indian Institute of Technology Madras, Chennai, India
| | - Saurav Dutta
- Department of Physics, Indian Institute of Technology Madras, Chennai, India
| | | | - Y Sajeev
- Theoretical Chemistry Section, Bhabha Atomic Research Centre, Mumbai, India
| | | | - G Aravind
- Department of Physics, Indian Institute of Technology Madras, Chennai, India
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7
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Barik S, Dutta S, Behera NR, Kushawaha RK, Sajeev Y, Aravind G. Ambient-light-induced intermolecular Coulombic decay in unbound pyridine monomers. Nat Chem 2022; 14:1098-1102. [PMID: 35909167 DOI: 10.1038/s41557-022-01002-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 06/16/2022] [Indexed: 11/09/2022]
Abstract
Intermolecular Coulombic decay (ICD) is a process whereby photoexcited molecules relax by ionizing their neighbouring molecules. ICD is efficient when intermolecular interactions are active and consequently it is observed only in weakly bound systems, such as clusters and hydrogen-bonded systems. Here we report an efficient ICD between unbound molecules excited at ambient-light intensities. On the photoexcitation of gas-phase pyridine monomers, well below the ionization threshold and at low laser intensities, we detected the parent and heavier-than-parent cations. The isotropic emission of slow electrons revealed ICD as the underlying process. π-π* excitation in unbounded pyridine monomers triggered an associative interaction between them, which leads to an efficient three-centre ICD. The cation resulting from the molecular association of the three pyridine centres relaxed through fragmentation. This below-threshold ionization under ambient light has implications for the understanding of radiation damage and astrochemistry.
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Affiliation(s)
- Saroj Barik
- Department of Physics, Indian Institute of Technology Madras, Chennai, India
| | - Saurav Dutta
- Department of Physics, Indian Institute of Technology Madras, Chennai, India
| | - Nihar Ranjan Behera
- Department of Physics, Indian Institute of Technology Madras, Chennai, India
| | | | - Y Sajeev
- Theoretical Chemistry Section, Bhabha Atomic Research Centre, Mumbai, India.
| | - G Aravind
- Department of Physics, Indian Institute of Technology Madras, Chennai, India.
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8
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Meyer KS, Westerfield JH, Johansen SL, Keane J, Wannenmacher AC, Crabtree KN. Rotational and Vibrational Spectra of the Pyridyl Radicals: A Coupled-Cluster Study. J Phys Chem A 2022; 126:3185-3197. [PMID: 35549287 DOI: 10.1021/acs.jpca.2c01761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pyridyl is a prototypical nitrogen-containing aromatic radical that may be a key intermediate in the formation of nitrogen-containing aromatic molecules under astrophysical conditions. On meteorites, a variety of complex molecules with nitrogen-containing rings have been detected with nonterrestrial isotopic abundances, and larger nitrogen-containing polycyclic aromatic hydrocarbons (PANHs) have been proposed to be responsible for certain unidentified infrared emission bands in the interstellar medium. In this work, the three isomers of pyridyl (2-, 3-, and 4-pyridyl) have been investigated with coupled cluster methods. For each species, structures were optimized at the CCSD(T)/cc-pwCVTZ level of theory and force fields were calculated at the CCSD(T)/ANO0 level of theory. Second-order vibrational perturbation theory (VPT2) was used to derive anharmonic vibrational frequencies and vibrationally corrected rotational constants, and resonances among vibrational states below 3500 cm-1 were treated variationally with the VPT2+K method. The results yield a complete set of spectroscopic parameters needed to simulate the pure rotational spectrum of each isomer, including electron-spin, spin-spin, and nuclear hyperfine interactions, and the calculated hyperfine parameters agree well with the limited available data from electron paramagnetic resonance spectroscopy. For the handful of experimentally measured vibrational frequencies determined from photoelectron spectroscopy and matrix isolation spectroscopy, the typical agreement is comparable to experimental uncertainty. The predicted parameters for rotational spectroscopy reported here can guide new experimental investigations into the yet-unobserved rotational spectra of these radicals.
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Affiliation(s)
- Kelly S Meyer
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - John H Westerfield
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Sommer L Johansen
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Jasmine Keane
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Anna C Wannenmacher
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Kyle N Crabtree
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
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9
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Barnum TJ, Siebert MA, Lee KLK, Loomis RA, Changala PB, Charnley SB, Sita ML, Xue C, Remijan AJ, Burkhardt AM, McGuire BA, Cooke IR. A Search for Heterocycles in GOTHAM Observations of TMC-1. J Phys Chem A 2022; 126:2716-2728. [PMID: 35442689 DOI: 10.1021/acs.jpca.2c01435] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have conducted an extensive search for nitrogen-, oxygen-, and sulfur-bearing heterocycles toward Taurus Molecular Cloud 1 (TMC-1) using the deep, broadband centimeter-wavelength spectral line survey of the region from the GOTHAM large project on the Green Bank Telescope. Despite their ubiquity in terrestrial chemistry, and the confirmed presence of a number of cyclic and polycyclic hydrocarbon species in the source, we find no evidence for the presence of any heterocyclic species. Here, we report the derived upper limits on the column densities of these molecules obtained by Markov Chain Monte Carlo (MCMC) analysis and compare this approach to traditional single-line upper limit measurements. We further hypothesize why these molecules are absent in our data, how they might form in interstellar space, and the nature of observations that would be needed to secure their detection.
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Affiliation(s)
- Timothy J Barnum
- Department of Chemistry, Union College, Schenectady, New York 12308, United States
| | - Mark A Siebert
- Department of Astronomy, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Kin Long Kelvin Lee
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Ryan A Loomis
- National Radio Astronomy Observatory, Charlottesville, Virginia 22903, United States
| | - P Bryan Changala
- Center for Astrophysics
- Harvard & Smithsonian, Cambridge, Massachusetts 02138, United States
| | - Steven B Charnley
- Astrochemistry Laboratory and the Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, United States
| | - Madelyn L Sita
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Ci Xue
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Anthony J Remijan
- National Radio Astronomy Observatory, Charlottesville, Virginia 22903, United States
| | - Andrew M Burkhardt
- Department of Physics, Wellesley College, 106 Central Street, Wellesley, Massachusetts 02481, United States
| | - Brett A McGuire
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.,National Radio Astronomy Observatory, Charlottesville, Virginia 22903, United States.,Center for Astrophysics
- Harvard & Smithsonian, Cambridge, Massachusetts 02138, United States
| | - Ilsa R Cooke
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
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10
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Edney MK, He W, Smith EF, Wilmot E, Reid J, Barker J, Griffiths RL, Alexander MR, Snape CE, Scurr DJ. Time resolved growth of (N)-polycyclic aromatic hydrocarbons in engine deposits uncovered with OrbiSIMS depth profiling. Analyst 2022; 147:3854-3866. [DOI: 10.1039/d2an00798c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Insoluble carbonaceous deposits were grown in internal combustion engine components and interrogated by OrbiSIMS depth profiling, and we uncovered the composition and proposed time resolved growth mechanisms of these materials.
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Affiliation(s)
- Max K. Edney
- Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, University Park, Nottingham, NG7 7RD, UK
| | - Wenshi He
- School of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Emily F. Smith
- Department of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Edward Wilmot
- Innospec Ltd., Oil Sites Road, Ellesmere Port, Cheshire, CH65 4EY, UK
| | - Jacqueline Reid
- Innospec Ltd., Oil Sites Road, Ellesmere Port, Cheshire, CH65 4EY, UK
| | - Jim Barker
- Innospec Ltd., Oil Sites Road, Ellesmere Port, Cheshire, CH65 4EY, UK
| | - Rian L. Griffiths
- School of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Morgan R. Alexander
- School of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Colin E. Snape
- Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, University Park, Nottingham, NG7 7RD, UK
| | - David J. Scurr
- School of Pharmacy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
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11
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Stein T, Bera PP, Lee TJ, Head-Gordon M. Molecular growth upon ionization of van der Waals clusters containing HCCH and HCN is a pathway to prebiotic molecules. Phys Chem Chem Phys 2020; 22:20337-20348. [PMID: 32895691 DOI: 10.1039/d0cp03350b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The growth mechanisms of organic molecules in an ionizing environment such as the interstellar medium are not completely understood. Here we examine by means of ab initio molecular dynamics (AIMD) simulations and density functional theory (DFT) computations the possibility of bond formation and molecular growth upon ionization of van der Waals clusters of pure HCN clusters, and mixed clusters of HCN and HCCH, both of which are widespread in the interstellar medium. Ionization of van der Waals clusters can potentially lead to growth in low temperature and low-density environments. Our results show, that upon ionization of the pure HCN clusters, strongly bound stable structures are formed that contain NH bonds, and growth beyond pairwise HCN molecules is seen only in a small percentage of cases. In contrast, mixed clusters, where HCCH is preferentially ionized over HCN, can grow up to 3 or 4 units long with new carbon-carbon and carbon-nitrogen covalent bonds. Moreover, cyclic molecules formed, such as the radical cation of pyridine, which is a prebiotic molecule. The results presented here are significant as they provide a feasible pathway for molecular growth of small organic molecules containing both carbon and nitrogen in cold and relatively denser environments such as in dense molecular clouds but closer to the photo-dissociation regions, and protoplanetary disks. In the mechanism we propose, first, a neutral van der Waals cluster is formed. Once the cluster is formed it can undergo photoionization which leads to chemical reactivity without any reaction barrier.
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Affiliation(s)
- Tamar Stein
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. and Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Partha P Bera
- Space Science and Astrobiology Division, NASA Ames Research Center, MS 245-6, Moffett Field, Mountain View, CA 94035, USA and Bay Area Environmental Research Institute, NASA Research Park, Moffett Field, CA 94035, USA
| | - Timothy J Lee
- Space Science and Astrobiology Division, NASA Ames Research Center, MS 245-6, Moffett Field, Mountain View, CA 94035, USA
| | - Martin Head-Gordon
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. and Department of Chemistry, University of California, Berkeley, CA 94720, USA
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12
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Stein T, Jose J. Molecular Formation upon Ionization of van der Waals Clusters and Implication to Astrochemistry. Isr J Chem 2020. [DOI: 10.1002/ijch.201900127] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Tamar Stein
- Fritz Haber Research Center for Molecular Dynamics The Hebrew University of Jerusalem Jerusalem 9190401 Israel
| | - Jeeno Jose
- Fritz Haber Research Center for Molecular Dynamics The Hebrew University of Jerusalem Jerusalem 9190401 Israel
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13
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Majer K, Signorell R, Heringa MF, Goldmann M, Hemberger P, Bodi A. Valence Photoionization of Thymine: Ionization Energies, Vibrational Structure, and Fragmentation Pathways from the Slow to the Ultrafast. Chemistry 2019; 25:14192-14204. [PMID: 31469456 DOI: 10.1002/chem.201903282] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Indexed: 11/06/2022]
Abstract
The photoionization of thymine has been studied by using vacuum ultraviolet radiation and imaging photoelectron photoion coincidence spectroscopy after aerosol flash vaporization and bulk evaporation. The two evaporation techniques have been evaluated by comparison of the photoelectron spectra and breakdown diagrams. The adiabatic ionization energies for the first four electronic states were determined to be 8.922±0.008, 9.851±0.008, 10.30±0.02, and 10.82±0.01 eV. Vibrational features have been assigned for the first three electronic states with the help of Franck-Condon factor calculations based on density functional theory and wave function theory vibrational analysis within the harmonic approximation. The breakdown diagram of thymine, as supported by composite method ab initio calculations, suggests that the main fragment ions are formed in sequential HNCO-, CO-, and H-loss dissociation steps from the thymine parent ion, with the first step corresponding to a retro-Diels-Alder reaction. The dissociation rate constants were extracted from the photoion time-of-flight distributions and used together with the breakdown curves to construct a statistical model to determine 0 K appearance energies of 11.15±0.16 and 11.95±0.09 eV for the m/z 83 and 55 fragment ions, respectively. These results have allowed us to revise previously proposed fragmentation mechanisms and to propose a model for the final, nonstatistical H-loss step in the breakdown diagram, yielding the m/z 54 fragment ion at an appearance energy of 13.24 eV.
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Affiliation(s)
- Katharina Majer
- Paul Scherrer Institute, 5232, Villigen, Switzerland.,Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zürich, 8093, Zürich, Switzerland
| | - Ruth Signorell
- Department of Chemistry and Applied Biosciences, Laboratory of Physical Chemistry, ETH Zürich, 8093, Zürich, Switzerland
| | - Maarten F Heringa
- Paul Scherrer Institute, 5232, Villigen, Switzerland.,Present address: Givaudan Schweiz AG, 8310, Kemptthal, Switzerland
| | - Maximilian Goldmann
- Gymnasium Lerbermatt, 3098, Köniz, Switzerland.,Hochschule Luzern - Technik & Architektur, 6048, Horw, Switzerland
| | | | - Andras Bodi
- Paul Scherrer Institute, 5232, Villigen, Switzerland
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14
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Kroonblawd MP, Lindsey RK, Goldman N. Synthesis of functionalized nitrogen-containing polycyclic aromatic hydrocarbons and other prebiotic compounds in impacting glycine solutions. Chem Sci 2019; 10:6091-6098. [PMID: 31360414 PMCID: PMC6585877 DOI: 10.1039/c9sc00155g] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 05/19/2019] [Indexed: 01/09/2023] Open
Abstract
Proteinogenic amino acids can be produced on or delivered to a planet via impacting abiotic sources and consequently were likely present before the emergence of life on Earth. However, the role that these materials played in prebiotic scenarios remains an open question, in part because little is known about the survivability and reactivity of astrophysical organic compounds upon impact with a planetary surface. To this end, we use a force-matched semi-empirical quantum simulation method to study impacts of aqueous proteinogenic amino acids at conditions reaching 48 GPa and 3000 K. Here, we probe a relatively unstudied mechanism for prebiotic synthesis where sudden heating and pressurization causes condensation of complex carbon-rich structures from mixtures of glycine, the simplest protein-forming amino acid. These carbon-containing clusters are stable on short timescales and undergo a fundamental structural transition upon expansion and cooling from predominantly sp3-bonded tetrahedral-like moieties to those that are more sp2-bonded and planar. The recovered sp2-bonded structures include large nitrogen containing polycyclic aromatic hydrocarbons (NPAHs) with a number of different functional groups and embedded bonded regions akin to oligo-peptides. A number of small organic molecules with prebiotic relevance are also predicted to form. This work presents an alternate route to gas-phase synthesis for the formation of NPAHs of high complexity and highlights the significance of both the thermodynamic path and local chemical self-assembly in forming prebiotic species during shock synthesis. Our results help determine the role of comets and other celestial bodies in both the delivery and synthesis of potentially significant life building compounds on early Earth.
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Affiliation(s)
- Matthew P Kroonblawd
- Physical and Life Sciences Directorate , Lawrence Livermore National Laboratory , Livermore , CA 94550 , USA .
| | - Rebecca K Lindsey
- Physical and Life Sciences Directorate , Lawrence Livermore National Laboratory , Livermore , CA 94550 , USA .
| | - Nir Goldman
- Physical and Life Sciences Directorate , Lawrence Livermore National Laboratory , Livermore , CA 94550 , USA .
- Department of Chemical Engineering , University of California , Davis , California 95616 , USA
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15
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Abplanalp MJ, Góbi S, Kaiser RI. On the formation and the isomer specific detection of methylacetylene (CH 3CCH), propene (CH 3CHCH 2), cyclopropane (c-C 3H 6), vinylacetylene (CH 2CHCCH), and 1,3-butadiene (CH 2CHCHCH 2) from interstellar methane ice analogues. Phys Chem Chem Phys 2019; 21:5378-5393. [PMID: 30221272 DOI: 10.1039/c8cp03921f] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pure methane (CH4) ices processed by energetic electrons under ultra-high vacuum conditions to simulate secondary electrons formed via galactic cosmic rays (GCRs) penetrating interstellar ice mantles have been shown to produce an array of complex hydrocarbons with the general formulae: CnH2n+2 (n = 4-8), CnH2n (n = 3-9), CnH2n-2 (n = 3-9), CnH2n-4 (n = 4-9), and CnH2n-6 (n = 6-7). By monitoring the in situ chemical evolution of the ice combined with temperature programmed desorption (TPD) studies and tunable single photon ionization coupled to a reflectron time-of-flight mass spectrometer, specific isomers of C3H4, C3H6, C4H4, and C4H6 were probed. These experiments confirmed the synthesis of methylacetylene (CH3CCH), propene (CH3CHCH2), cyclopropane (c-C3H6), vinylacetylene (CH2CHCCH), 1-butyne (HCCC2H5), 2-butyne (CH3CCCH3), 1,2-butadiene (H2CCCH(CH3)), and 1,3-butadiene (CH2CHCHCH2) with yields of 2.17 ± 0.95 × 10-4, 3.7 ± 1.5 × 10-3, 1.23 ± 0.77 × 10-4, 1.28 ± 0.65 × 10-4, 4.01 ± 1.98 × 10-5, 1.97 ± 0.98 × 10-4, 1.90 ± 0.84 × 10-5, and 1.41 ± 0.72 × 10-4 molecules eV-1, respectively. Mechanistic studies exploring the formation routes of methylacetylene, propene, and vinylacetylene were also conducted, and revealed the additional formation of the 1,2,3-butatriene isomer. Several of the above isomers, methylacetylene, propene, vinylacetylene, and 1,3-butadiene, have repeatedly been shown to be important precursors in the formation of polycyclic aromatic hydrocarbons (PAHs), but until now their interstellar synthesis has remained elusive.
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Affiliation(s)
- Matthew J Abplanalp
- W. M. Keck Research Laboratory in Astrochemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
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16
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Leach S, Jones NC, Hoffmann SV, Un S. Isoquinoline gas-phase absorption spectrum in the vacuum ultraviolet between 3.7 and 10.7 eV. New valence and Rydberg electronic states. RSC Adv 2019; 9:5121-5141. [PMID: 35514650 PMCID: PMC9060705 DOI: 10.1039/c8ra09725a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 02/05/2019] [Indexed: 12/25/2022] Open
Abstract
VUV photons from a synchrotron source were used to record the gas-phase absorption spectrum of isoquinoline over the range 3.5 to 10.7 eV. The rich spectrum exhibits both broad and sharp features, of varying intensities, that are analyzed into eight valence and eight Rydberg transitions. Previous data on the valence transitions of isoquinoline were essentially limited to solution spectra up to 5.4 eV. Our study increases their number considerably. The features in the 3.96 eV region are discussed in terms of vibronic coupling between the nπ* 11A′′ and ππ* 21A′ valence electronic states. The intensities of some spectral features are augmented by collective π-electron modes considered to be of plasmon-type. Assignments of the valence transitions were facilitated by our DFT calculations and by earlier Pariser–Parr–Pople MO calculations. The calculation results are compared and their relative value is discussed. The DFT calculations reproduce very well a number of experimentally determined properties of the ground state of isoquinoline, in particular its bond distances and angles, rotational constants, vibrational frequencies and dipole moment. No Rydberg series of isoquinoline have previously been observed. Three of the newly observed Rydberg series converge to the D0 electronic ground state of the ion, while two converge to the D1 and three to the D3 excited electronic states of the cation. Astrophysical applications of the VUV absorption spectrum of isoquinoline, in particular the measured absorption cross-sections, are briefly discussed. A comparison between the absorption spectra of isoquinoline and quinoline highlights their similarities and differences, related to their respective molecular orbitals. VUV photons from a synchrotron source were used to record the gas-phase absorption spectrum of isoquinoline over the range 3.5 to 10.7 eV.![]()
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Affiliation(s)
- Sydney Leach
- LERMA
- Observatoire de Paris
- PSL Research University
- CNRS
- Sorbonne Universités
| | - Nykola C. Jones
- ISA
- Department of Physics and Astronomy
- Aarhus University
- Denmark
| | | | - Sun Un
- Institute for Integrative Biology of the Cell (I2BC)
- Department of Biochemistry
- Biophysics and Structural Biology
- Université Paris-Saclay
- CEA
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17
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Bright CC, Prendergast MB, Kelly PD, Bezzina JP, Blanksby SJ, da Silva G, Trevitt AJ. Highly efficient gas-phase reactivity of protonated pyridine radicals with propene. Phys Chem Chem Phys 2018; 19:31072-31084. [PMID: 29152628 DOI: 10.1039/c7cp06644a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Small nitrogen containing heteroaromatics are fundamental building blocks for many biological molecules, including the DNA nucleotides. Pyridine, as a prototypical N-heteroaromatic, has been implicated in the chemical evolution of many extraterrestrial environments, including the atmosphere of Titan. This paper reports on the gas-phase ion-molecule reactions of the three dehydro-N-pyridinium radical cation isomers with propene. Photodissociation ion-trap mass spectrometry experiments are used to measure product branching ratios and reaction kinetics. Reaction efficiencies for 2-dehydro-N-pyridinium, 3-dehydro-N-pyridinium and 4-dehydro-N-pyridinium with propene are 70%, 47% and 41%, respectively. The m/z 106 channel is the major product channel across all cases and assigned 2-, 3-, and 4-vinylpyridinium for each reaction. The m/z 93 channel is also significant and assigned the 2-, 3-, and 4-N-protonated-picolyl radical cation for each case. H-Abstraction from propene is not competitive under experimental conditions. Potential energy schemes, at the M06-2X/6-31(2df,p) level of theory and basis set, are described to assist in rationalising observed product branching ratios and elucidating possible reaction mechanisms. Reaction barriers to the production of vinylpyridinium (m/z 106) + CH3 are the lowest identified for the 3- and 4-dehydro-N-pyridinium reactions, in support of the observed dominance of the m/z 106 ion signal. Ethylene loss via ring-mediated H-transfer along the propyl group is found to be the lowest energy pathway for the 2-dehydro-N-pyridinium reaction, suggesting a preference toward m/z 93 (N-protonated-picolyl radical cation) over the experimentally observed products. Entropic bottle-necks along the m/z 93 pathway however, associated with ring-mediated H-atom transfer, are responsible for the dominance of m/z 106 in the 2-dehydro-N-pyridinium + propene reaction. For all three isomers, computed barriers for all observed reaction channels were below the entrance channel, suggesting these reactions can contribute to molecular weight growth in extraterrestrial environments with accelerated reaction rates in low temperature regions of space.
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Affiliation(s)
- Cameron C Bright
- School of Chemistry, University of Wollongong, Wollongong, NSW 2522, Australia.
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18
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Bouwman J, Bodi A, Hemberger P. Nitrogen matters: the difference between PANH and PAH formation. Phys Chem Chem Phys 2018; 20:29910-29917. [DOI: 10.1039/c8cp05830j] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Because of the large stability of the nitrile group, the N-substituted aromatic molecule quinoline does not form in the phenyl + acrylonitrile reaction, in contrast to naphthalene formation in the isoelectronic phenyl + vinylacetylene reaction.
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Affiliation(s)
- Jordy Bouwman
- Sackler Laboratory for Astrophysics
- Leiden Observatory
- Leiden University
- NL 2300 RA Leiden
- The Netherlands
| | - Andras Bodi
- Laboratory for Synchrotron Radiation and Femtochemistry
- Paul Scherrer Institute
- 5232 Villigen
- Switzerland
| | - Patrick Hemberger
- Laboratory for Synchrotron Radiation and Femtochemistry
- Paul Scherrer Institute
- 5232 Villigen
- Switzerland
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19
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Mebel AM, Landera A, Kaiser RI. Formation Mechanisms of Naphthalene and Indene: From the Interstellar Medium to Combustion Flames. J Phys Chem A 2017; 121:901-926. [DOI: 10.1021/acs.jpca.6b09735] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alexander M. Mebel
- Department
of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Alexander Landera
- Chemical
Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Ralf I. Kaiser
- Department
of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
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20
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Parker DSN, Kaiser RI. On the formation of nitrogen-substituted polycyclic aromatic hydrocarbons (NPAHs) in circumstellar and interstellar environments. Chem Soc Rev 2017; 46:452-463. [DOI: 10.1039/c6cs00714g] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The chemical evolution of extraterrestrial environments leads to the formation of nitrogen substituted polycyclic aromatic hydrocarbons (NPAHs) via gas phase radical mediated aromatization reactions.
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Affiliation(s)
| | - Ralf I. Kaiser
- Department of Chemistry
- University of Hawai’i at Manoa
- Honolulu
- USA
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21
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22
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Parker DSN, Yang T, Dangi BB, Kaiser RI, Bera PP, Lee TJ. LOW TEMPERATURE FORMATION OF NITROGEN-SUBSTITUTED POLYCYCLIC AROMATIC HYDROCARBONS (PANHs)—BARRIERLESS ROUTES TO DIHYDRO(iso)QUINOLINES. ACTA ACUST UNITED AC 2015. [DOI: 10.1088/0004-637x/815/2/115] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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23
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Mehta-Hurt DN, Korn JA, Navotnaya P, Parobek AP, Clayton RM, Zwier TS. The spectroscopy and photochemistry of quinioline structural isomers: (E)- and (Z)-phenylvinylnitrile. J Chem Phys 2015; 143:074304. [PMID: 26298131 DOI: 10.1063/1.4928191] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
In Titan's atmosphere, photochemical pathways that lead to nitrogen heteroaromatics may incorporate photoisomerization of their structural isomers as a final step. (E)- and (Z)-phenylvinylnitrile ((E)- and (Z)-PVN, C6H5-CH=CHCN) are structural isomers of quinoline that themselves possess extensive absorptions in the ultraviolet, and thus may engage in such photoisomerization pathways. The present study explores the vibronic spectroscopy and photo-induced isomerization of gas-phase (E)- and (Z)-PVN in the 33,600-35,850 cm(-1) region under jet-cooled conditions. The S0-S1 origins for (E)- and (Z)-PVN have been identified at 33 827 cm(-1) and 33 707 cm(-1), respectively. Isomer-specific UV-UV hole-burning and UV depletion spectra reveal sharp vibronic structure that extends over almost 2000 cm(-1), with thresholds for fast non-radiative decay identified by a comparison between hole-burning and UV depletion spectra. Dispersed fluorescence spectra of the two isomers enable the assignment of many low frequency transitions in both molecules, aided by harmonic frequency calculations (B3LYP/6-311++G(d,p)) and a comparison with the established spectroscopy of phenylvinylacetylene, the ethynyl counterpart to PVN. Both isomers are proven to be planar in both the S0 ground and S1 electronic excited states. (E)-PVN exhibits extensive Duschinsky mixing involving out-of-plane modes whose frequencies and character change significantly in the ππ* transition, which modulates the degree of single- and double-bond character along the vinylnitrile substituent. This same mixing is much less evident in (Z)-PVN. The spectroscopic characterization of (E)- and (Z)-PVN served as the basis for photoisomerization experiments using ultraviolet hole-filling spectroscopy carried out in a reaction tube affixed to the pulsed valve. Successful interconversion between (E) and (Z)-PVN was demonstrated via ultraviolet hole-filling experiments. Photoexcitation of (E)- and (Z)-PVN at their respective S0-S1 origins failed to produce quinoline, a simple polycyclic aromatic nitrogen heterocylcle, within the detection sensitivity of our experiments. Stationary points along the potential energy surface associated with (Z)-PVN → quinoline isomerization showed a barrier of 93 kcal/mol associated with the first step in the isomerization process, slowing the interconversion process at the excitation energies used (96 kcal/mol) to timescales beyond those probed in the present experiment.
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Affiliation(s)
- Deepali N Mehta-Hurt
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA
| | - Joseph A Korn
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA
| | - Polina Navotnaya
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA
| | - Alexander P Parobek
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA
| | - Rachel M Clayton
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA
| | - Timothy S Zwier
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907-2084, USA
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