1
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Lozano AI, Kumar S, Pereira PJS, Kerkeni B, García G, Limão-Vieira P. Low-lying Negative Ion States Probed in Potassium - Ethanol Collisions. Chemphyschem 2024; 25:e202400314. [PMID: 38630012 DOI: 10.1002/cphc.202400314] [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: 03/20/2024] [Revised: 04/17/2024] [Indexed: 05/23/2024]
Abstract
Dissociative electron transfer in collisions between neutral potassium atoms and neutral ethanol molecules yields mainly OH-, followed by C2H5O-, O-, CH3 - and CH2 -. The dynamics of negative ions have been investigated by recording time-of-flight mass spectra in a wide range of collision energies from 17.5 to 350 eV in the lab frame, where the branching ratios show a relevant energy dependence for low/intermediate collision energies. The dominant fragmentation channel in the whole energy range investigated has been assigned to the hydroxyl anion in contrast to oxygen anion from dissociative electron attachment (DEA) experiments. This result shows the relevant role of the electron donor in the vicinity of the temporary negative ion formed allowing access to reactions which are not thermodynamically attained in DEA experiments. The electronic state spectroscopy of such negative ions, was obtained from potassium cation energy loss spectra in the forward scattering direction at 205 eV impact energy, showing a prevalent Feshbach resonance at 9.36±0.10 eV withσ O H * / σ C H * ${{\sigma }_{OH}^{^{\ast}}/{\sigma }_{CH}^{^{\ast}}}$ character, while a less pronouncedσ O H * ${{\sigma }_{OH}^{^{\ast}}}$ contribution assigned to a shape resonance has been obtained at 3.16±0.10 eV. Quantum chemical calculations for the lowest-lying unoccupied molecular orbitals in the presence of a potassium atom have been performed to support the experimental findings.
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Affiliation(s)
- Ana Isabel Lozano
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, 31028 Toulouse, France
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, 94720, California, USA
| | - Sarvesh Kumar
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, 31028 Toulouse, France
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, 94720, California, USA
| | - Pedro J S Pereira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, 31028 Toulouse, France
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, 94720, California, USA
- Department of Mathematics, Instituto Superior de Engenharia de Lisboa, R. Conselheiro Emídio Navarro 1, 1959-007, Lisboa, Portugal
| | - Boutheïna Kerkeni
- ISAMM, Université de la Manouba, La Manouba, 2010, Tunisia
- Département de Physique, LPMC, Faculté des Sciences de Tunis, Université de Tunis el Manar, Tunis, 2092, Tunisia
| | - Gustavo García
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (CSIC), Serrano 113-bis, 28006, Madrid, Spain
| | - Paulo Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516, Caparica, Portugal
- Institut de Recherche en Astrophysique et Planétologie (IRAP), Université Toulouse III - Paul Sabatier, CNRS, CNES, 9 Avenue du Colonel Roche, 31028 Toulouse, France
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, 94720, California, USA
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2
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Kumar S, Hoshino M, Kerkeni B, García G, Limão-Vieira P. Isotope Effect in D 2O Negative Ion Formation in Electron Transfer Experiments: DO-D Bond Dissociation Energy. J Phys Chem Lett 2023; 14:5362-5369. [PMID: 37276433 PMCID: PMC10278136 DOI: 10.1021/acs.jpclett.3c00786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 05/31/2023] [Indexed: 06/07/2023]
Abstract
H2O/D2O negative ion time-of-flight mass spectra from electron transfer processes at different collision energies with neutral potassium yield OH-/OD-, O-, and H-/D-. The branching ratios show a relevant energy dependence with an important isotope effect in D2O. Electronic state spectroscopy of water has been further investigated by recording potassium cation energy loss spectra in the forward scattering direction at an impact energy of 205 eV (lab frame), with quantum chemical calculations for the lowest-lying unoccupied molecular orbitals in the presence of a potassium atom supporting most of the experimental findings. The DO-D bond dissociation energy has been determined for the first time to be 5.41 ± 0.10 eV. The collision dynamics revealed the character of the singly excited (1b2-1) molecular orbital and doubly excited states in such K-H2O and K-D2O collisions.
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Affiliation(s)
- Sarvesh Kumar
- Atomic
and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - Masamitsu Hoshino
- Department
of Materials and Life Sciences, Sophia University, Tokyo 102-8554, Japan
| | - Boutheïna Kerkeni
- ISAMM,
Université de la Manouba, La Manouba 2010, Tunisia
- Département
de Physique, LPMC, Faculté des Sciences de Tunis, Université de Tunis el Manar, Tunis 2092, Tunisia
| | - Gustavo García
- Instituto
de Física Fundamental, Consejo Superior de Investigaciones
Científicas (CSIC), Serrano 113-bis, 28006 Madrid, Spain
| | - Paulo Limão-Vieira
- Atomic
and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
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3
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Kumar S, Kilich T, Łabuda M, García G, Limão-Vieira P. Anionic states of C 6Cl 6 probed in electron transfer experiments. Phys Chem Chem Phys 2021; 24:366-374. [PMID: 34889910 DOI: 10.1039/d1cp04500h] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
This is the first comprehensive investigation on the anionic species formed during collisions of fast neutral potassium (K) atoms with neutral hexachlorobenzene (C6Cl6) molecules in the laboratory frame range from 10 up to 100 eV. In such ion-pair formation experiments we also report a novel K+ energy loss spectrum obtained in the forward scattering giving evidence of the most accessible electronic states. The vertical electron affinity of (-3.76 ± 0.20) eV has been obtained and assigned to a purely repulsive transition from the C6Cl6 ground state to a state of the temporary negative ion yielding Cl- formation. These experimental findings are also supported by state-of-the art theoretical calculations on the electronic structure of C6Cl6 in the presence of a potassium atom and are used for analysing the lowest unoccupied molecular orbitals participating in the collision process. From the time-of-flight mass spectra recorded in the wide collision energy range, more than 80% of the total anion yield is due to the undissociated parent anion C6Cl6-, C6Cl5- and Cl- formation. Other fragment anions such as C6Cl4-, C3Cl2-, C2Cl- and Cl2- that undergo complex internal reactions with the temporary negative ion formed after electron transfer account for less than 20% of the total yield. The joint experimental and theoretical methodologies employed in these electron transfer studies provide the most comprehensive and unique assignments of the hexachlorobenzene anionic species and the role of C6Cl6 electronic states in collision induced dissociation to date.
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Affiliation(s)
- S Kumar
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
| | - T Kilich
- Department of Theoretical Physics and Quantum Information, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland
| | - M Łabuda
- Department of Theoretical Physics and Quantum Information, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland.,BioTechMed, Gdańsk University of Technology, Gdańsk, Poland
| | - G García
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (CSIC), Serrano 113-bis, 28006 Madrid, Spain
| | - P Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
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4
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da Silva FF, Cunha T, Rebelo A, Gil A, Calhorda MJ, García G, Ingólfsson O, Limão-Vieira P. Electron-Transfer-Induced Side-Chain Cleavage in Tryptophan Facilitated through Potassium-Induced Transition-State Stabilization in the Gas Phase. J Phys Chem A 2021; 125:2324-2333. [DOI: 10.1021/acs.jpca.1c00690] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Filipe Ferreira da Silva
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - Tiago Cunha
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - Andre Rebelo
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - Adrià Gil
- BioISI -Biosystems & Integrative Sciences Institute, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
- CIC nanoGUNE BRTA, Tolosa Hiribidea, 76, E-20018 Donostia − San Sebastián, Euskadi, Spain
| | - Maria José Calhorda
- BioISI -Biosystems & Integrative Sciences Institute, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
| | - Gustavo García
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (CSIC), Serrano 113-bis, 28006 Madrid, Spain
| | - Oddur Ingólfsson
- Chemistry and Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavik, Iceland
| | - Paulo Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
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5
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Regeta K, Kumar S, Cunha T, Mendes M, Lozano AI, Pereira PJS, García G, Moutinho AMC, Bacchus-Montabonel MC, Limão-Vieira P. Combined Experimental and Theoretical Studies on Electron Transfer in Potassium Collisions with CCl 4. J Phys Chem A 2020; 124:3220-3227. [PMID: 32233369 DOI: 10.1021/acs.jpca.0c02076] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Negative ion formation in electron transfer experiments from fast neutral potassium (K) atom collisions with neutral tetrachloromethane (CCl4) molecules has been investigated in the laboratory frame range of 8-1000 eV. Comprehensive calculations on the electronic structure were performed for CCl4 in the presence of a potassium atom and used to help analyze the lowest unoccupied molecular orbitals participating in the collision process. Additionally, K+ energy loss produced in the forward direction has served to further our knowledge on the electronic state spectroscopy of CCl4. A vertical electron affinity of -0.79 ± 0.20 eV has been obtained and assigned to a purely repulsive transition from CCl4 ground state to the 2T2 state of the temporary negative ion yielding Cl- formation. Other features in the energy loss spectrum were observed for the first time and related to Cl2-, CCl2-, and CCl3- formation. Special attention is also given to the unresolved feature corresponding to a positive electron affinity of 0.24 ± 0.2 eV, assigned to a vibrationally hot transition from CCl4 ground state into the triply degenerate 2T2 excited state of the negative ion. The combined time-of-flight mass spectrometry together with K+ energy loss data represents the most comprehensive assignment of the tetrachloromethane anion yields and the role of CCl4 electronic states in collision induced dissociation to date.
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Affiliation(s)
- K Regeta
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - S Kumar
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - T Cunha
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - M Mendes
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - A I Lozano
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - P J S Pereira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.,Department of Mathematics, Instituto Superior de Engenharia de Lisboa, R. Conselheiro Emídio Navarro 1, 1959-007 Lisboa, Portugal
| | - G García
- Instituto de Fı́sica Fundamental, Consejo Superior de Investigaciones Cientı́ficas (CSIC), Serrano 113-bis, 28006 Madrid, Spain
| | - A M C Moutinho
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - M-C Bacchus-Montabonel
- Institut Lumière Matière, CNRS, Université Claude Bernard Lyon 1, 69622 Villeurbanne, France
| | - P Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
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6
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Sahakyan AB, Mahtey A, Kawasaki F, Balasubramanian S. A Spontaneous Ring-Opening Reaction Leads to a Repair-Resistant Thymine Oxidation Product in Genomic DNA. Chembiochem 2020; 21:320-323. [PMID: 31386787 DOI: 10.1002/cbic.201900484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Indexed: 11/09/2022]
Abstract
The alphabet of modified DNA bases goes beyond the conventional four letters, with biological roles being found for many such modifications. Herein, we describe the observation of a modified thymine base that arises from spontaneous N1 -C2 ring opening of the oxidation product 5-formyl uracil, after N3 deprotonation. We first observed this phenomenon in silico through ab initio calculations, followed by in vitro experiments to verify its formation at a mononucleoside level and in a synthetic DNA oligonucleotide context. We show that the new base modification (Trex , thymine ring expunged) can form under physiological conditions, and is resistant to the action of common repair machineries. Furthermore, we found cases of the natural existence of Trex while screening a number of human cell types and mESC (E14), thus suggesting potential biological relevance of this modification.
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Affiliation(s)
- Aleksandr B Sahakyan
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
- Present address: MRC WIMM Centre for Computational Biology, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department of Medicine, University of Oxford, Headington, Oxford, OX3 9DS, UK
| | - Areeb Mahtey
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Fumiko Kawasaki
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
- Present address: RIKEN, Center for Advanced Intelligence Project, Tokyo, 103-0027, Japan
| | - Shankar Balasubramanian
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
- Cancer Research (UK), Cambridge Institute, Li Ka Shing Centre, University of Cambridge, Robinson Way, Cambridge, CB2 0RE, UK
- School of Clinical Medicine, University of Cambridge, Cambridge, CB2 0SP, UK
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7
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Electron Transfer Induced Decomposition in Potassium-Nitroimidazoles Collisions: An Experimental and Theoretical Work. Int J Mol Sci 2019; 20:ijms20246170. [PMID: 31817793 PMCID: PMC6940910 DOI: 10.3390/ijms20246170] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 11/13/2019] [Accepted: 11/28/2019] [Indexed: 11/21/2022] Open
Abstract
Electron transfer induced decomposition mechanism of nitroimidazole and a selection of analogue molecules in collisions with neutral potassium (K) atoms from 10 to 1000 eV have been thoroughly investigated. In this laboratory collision regime, the formation of negative ions was time-of-flight mass analyzed and the fragmentation patterns and branching ratios have been obtained. The most abundant anions have been assigned to the parent molecule and the nitrogen oxide anion (NO2–) and the electron transfer mechanisms are comprehensively discussed. This work focuses on the analysis of all fragment anions produced and it is complementary of our recent work on selective hydrogen loss from the transient negative ions produced in these collisions. Ab initio theoretical calculations were performed for 4-nitroimidazole (4NI), 2-nitroimidazole (2NI), 1-methyl-4- (Me4NI) and 1-methyl-5-nitroimidazole (Me5NI), and imidazole (IMI) in the presence of a potassium atom and provided a strong basis for the assignment of the lowest unoccupied molecular orbitals accessed in the collision process.
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8
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The Role of Electron Transfer in the Fragmentation of Phenyl and Cyclohexyl Boronic Acids. Int J Mol Sci 2019; 20:ijms20225578. [PMID: 31717298 PMCID: PMC6888488 DOI: 10.3390/ijms20225578] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Revised: 11/05/2019] [Accepted: 11/06/2019] [Indexed: 11/17/2022] Open
Abstract
In this study, novel measurements of negative ion formation in neutral potassium-neutral boronic acid collisions are reported in electron transfer experiments. The fragmentation pattern of phenylboronic acid is comprehensively investigated for a wide range of collision energies, i.e., from 10 to 1000 eV in the laboratory frame, allowing some of the most relevant dissociation channels to be probed. These studies were performed in a crossed molecular beam set up using a potassium atom as an electron donor. The negative ions formed in the collision region were mass analysed with a reflectron time-of-flight mass spectrometer. In the unimolecular decomposition of the temporary negative ion, the two most relevant yields were assigned to BO- and BO2-. Moreover, the collision-induced reaction was shown to be selective, i.e., at energies below 100 eV, it mostly formed BO-, while at energies above 100 eV, it mostly formed BO2-. In order to further our knowledge on the complex internal reaction mechanisms underlying the influence of the hybridization state of the boron atom, cyclohexylboronic acid was also investigated in the same collision energy range, where the main dissociation channel yielded BO2-. The experimental results for phenyl boronic acid are supported by ab initio theoretical calculations of the lowest unoccupied molecular orbitals (LUMOs) accessed in the collision process.
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9
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Mendes M, Probst M, Maihom T, García G, Limão-Vieira P. Selective Bond Excision in Nitroimidazoles by Electron Transfer Experiments. J Phys Chem A 2019; 123:4068-4073. [PMID: 30995841 DOI: 10.1021/acs.jpca.9b02064] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have performed comprehensive charge-transfer experiments yielding negative ion formation in collisions of fast neutral potassium atoms with nitroimidazole and methylated derivative molecules. The anionic pattern reveals that in the unimolecular decomposition of the precursor parent anion, single and multiple bond cleavages are attained. Selective excision of hydrogen atoms from the N1 position in 4-nitroimidazole (4NI) is completely blocked upon methylation in 1-methyl-4-nitroimidazole (1m4NI) and 1-methyl-5-nitroimidazole (1m5NI). Additionally, only 4NI and 2-nitroimidazole (2NI) are efficient in selectively producing neutral •OH and NO• radicals in contrast to 1m4NI and 1m5NI. These findings present a novel experimental evidence of selective chemical bond breaking by just tuning the proper collision energy in atom-molecule collision experiments. The present work contributes to the current need of pinpointing a class of charge-transfer collisions that exhibit selective reactivity of the kind demonstrated here, extending to tailored chemical control for different applications such as tumor radiation therapy through nitroimidazole-based radiosensitization.
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Affiliation(s)
- M Mendes
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics , Universidade NOVA de Lisboa , Campus de Caparica , 2829-516 Caparica , Portugal.,Instituto de Física Fundamental , Consejo Superior de Investigaciones Científicas , Serrano 113-bis , 28006 Madrid , Spain
| | - M Probst
- Institut für Ionenphysik und Angewandte Physik , Leopold Franzens Universität Innsbruck , Technikerstrasse 25 , 6020 Innsbruck , Austria
| | - T Maihom
- Department of Chemistry, Faculty of Liberal Arts and Science , Kasetsart University , Kamphaeng Saen Campus , Nakhon Pathom 73140 , Thailand
| | - G García
- Instituto de Física Fundamental , Consejo Superior de Investigaciones Científicas , Serrano 113-bis , 28006 Madrid , Spain
| | - P Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics , Universidade NOVA de Lisboa , Campus de Caparica , 2829-516 Caparica , Portugal
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10
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Mendes M, Pamplona B, Kumar S, da Silva FF, Aguilar A, García G, Bacchus-Montabonel MC, Limao-Vieira P. Ion-Pair Formation in Neutral Potassium-Neutral Pyrimidine Collisions: Electron Transfer Experiments. Front Chem 2019; 7:264. [PMID: 31058139 PMCID: PMC6482480 DOI: 10.3389/fchem.2019.00264] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 04/01/2019] [Indexed: 11/13/2022] Open
Abstract
We report novel data on ion-pair formation in hyperthermal (30–800 eV) neutral potassium collisions with neutral pyrimidine (Pyr, C4H4N2) molecules. In this collision regime, negative ions formed by electron transfer from the alkali atom to the target molecule were time-of-flight mass analyzed and the fragmentation patterns and branching ratios have been obtained. The most abundant product anions have been assigned to CN− and C2H− and the electron transfer mechanisms are comprehensively discussed. Particular importance is also given to the efficient loss of integrity of the pyrimidine ring in the presence of an extra electron, which is in contrast to dissociative electron attachment experiments yielding the dehydrogenated parent anion. Theoretical calculations were performed for pyrimidine in the presence of a potassium atom and provided a strong basis for the assignment of the lowest unoccupied molecular orbitals accessed in the collision process. In order to further our knowledge about the collision dynamics, potassium cation (K+) energy loss spectrum has been obtained and within this context, we also discuss the role of the accessible electronic states. A vertical electron affinity of (−5.69 ± 0.20) eV was obtained and may be assigned to a π3*(b1) state that leads to CN− formation.
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Affiliation(s)
- Mónica Mendes
- Atomic and Molecular Collisions Laboratory, Centre of Physics and Technological Research (CEFITEC), Department of Physics, Universidade NOVA de Lisboa, Costa de Caparica, Portugal.,Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Beatriz Pamplona
- Atomic and Molecular Collisions Laboratory, Centre of Physics and Technological Research (CEFITEC), Department of Physics, Universidade NOVA de Lisboa, Costa de Caparica, Portugal
| | - Sarvesh Kumar
- Atomic and Molecular Collisions Laboratory, Centre of Physics and Technological Research (CEFITEC), Department of Physics, Universidade NOVA de Lisboa, Costa de Caparica, Portugal
| | - Filipe Ferreira da Silva
- Atomic and Molecular Collisions Laboratory, Centre of Physics and Technological Research (CEFITEC), Department of Physics, Universidade NOVA de Lisboa, Costa de Caparica, Portugal
| | - Antonio Aguilar
- Departament de Ciència de Materials i Química Física, Universitat de Barcelona, Barcelona, Spain
| | - Gustavo García
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | | | - Paulo Limao-Vieira
- Atomic and Molecular Collisions Laboratory, Centre of Physics and Technological Research (CEFITEC), Department of Physics, Universidade NOVA de Lisboa, Costa de Caparica, Portugal
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11
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Cunha T, Mendes M, Ferreira da Silva F, Eden S, García G, Limão-Vieira P. Communication: Site-selective bond excision of adenine upon electron transfer. J Chem Phys 2018; 148:021101. [PMID: 29331144 DOI: 10.1063/1.5018401] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
This work demonstrates that selective excision of hydrogen atoms at a particular site of the DNA base adenine can be achieved in collisions with electronegative atoms by controlling the impact energy. The result is based on analysing the time-of-flight mass spectra yields of potassium collisions with a series of labeled adenine derivatives. The production of dehydrogenated parent anions is consistent with neutral H loss either from selective breaking of C-H or N-H bonds. These unprecedented results open up a new methodology in charge transfer collisions that can initiate selective reactivity as a key process in chemical reactions that are dominant in different areas of science and technology.
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Affiliation(s)
- T Cunha
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| | - M Mendes
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| | - F Ferreira da Silva
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
| | - S Eden
- School of Physical Sciences, The Open University, Walton Hall, MK7 6AA Milton Keynes, United Kingdom
| | - G García
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas, Serrano 113-bis, 28006 Madrid, Spain
| | - P Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
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12
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Cunha T, Mendes M, Ferreira da Silva F, Eden S, García G, Bacchus-Montabonel MC, Limão-Vieira P. Electron transfer driven decomposition of adenine and selected analogs as probed by experimental and theoretical methods. J Chem Phys 2018; 148:134301. [PMID: 29626890 DOI: 10.1063/1.5021888] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report on a combined experimental and theoretical study of electron-transfer-induced decomposition of adenine (Ad) and a selection of analog molecules in collisions with potassium (K) atoms. Time-of-flight negative ion mass spectra have been obtained in a wide collision energy range (6-68 eV in the centre-of-mass frame), providing a comprehensive investigation of the fragmentation patterns of purine (Pu), adenine (Ad), 9-methyl adenine (9-mAd), 6-dimethyl adenine (6-dimAd), and 2-D adenine (2-DAd). Following our recent communication about selective hydrogen loss from the transient negative ions (TNIs) produced in these collisions [T. Cunha et al., J. Chem. Phys. 148, 021101 (2018)], this work focuses on the production of smaller fragment anions. In the low-energy part of the present range, several dissociation channels that are accessible in free electron attachment experiments are absent from the present mass spectra, notably NH2 loss from adenine and 9-methyl adenine. This can be understood in terms of a relatively long transit time of the K+ cation in the vicinity of the TNI tending to enhance the likelihood of intramolecular electron transfer. In this case, the excess energy can be redistributed through the available degrees of freedom inhibiting fragmentation pathways. Ab initio theoretical calculations were performed for 9-methyl adenine (9-mAd) and adenine (Ad) in the presence of a potassium atom and provided a strong basis for the assignment of the lowest unoccupied molecular orbitals accessed in the collision process.
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Affiliation(s)
- T Cunha
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - M Mendes
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - F Ferreira da Silva
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
| | - S Eden
- School of Physical Sciences, The Open University, Walton Hall, MK7 6AA Milton Keynes, United Kingdom
| | - G García
- Instituto de Física Fundamental, Consejo Superior de Investigaciones Científicas (CSIC), Serrano 113-bis, 28006 Madrid, Spain
| | - M-C Bacchus-Montabonel
- Institut Lumiére Matiére, Université Lyon, Université Claude Bernard Lyon 1, CNRS, 69622 Villeurbanne, France
| | - P Limão-Vieira
- Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal
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Bacchus-Montabonel MC. Proton-Induced Collisions on Potential Prebiotic Species. ORIGINS LIFE EVOL B 2016; 46:361-368. [PMID: 27029793 DOI: 10.1007/s11084-016-9487-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 12/14/2015] [Indexed: 11/25/2022]
Abstract
With regard to the fascinating question of the origin of life, special interest has been devoted to potential prebiotic molecules which could drive the emergence of life. In the widely discussed hypothesis of a possible exogen apparition of life, the transport of those prebiotic species and their survival under spatial conditions is of strong interest. In particular their stability under solar radiation or in collisions with bare nucleus has to be considered. In that sense, taking account of the abundance of protons in ionized clouds of the interstellar medium, we have developed a detailed theoretical study of the charge transfer collision dynamics induced by impact of protons on a series of possible prebiotic compounds. Three main types of molecules have been considered: first of all the DNA and RNA building blocks with on a one hand the nucleobases uracil and thymine, and on the other hand the 2-deoxy-D-ribose sugar skeleton in its furanose and pyranose forms. The study has been extended to the 2-aminooxazole suggested to be a possible precursor of RNA nucleotides. The theoretical treatment involves ab-initio quantum chemistry molecular calculations followed by a semiclassical collision dynamics. Some qualitative trends may be suggested for the proton-induced damage of such prebiotic species.
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