Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical Calculations
We report absolute photoabsorption cross sections for gas-phase 2- and 5-bromopyrimidine in the 3.7–10.8 eV energy range, in a joint theoretical and experimental study. The measurements were carried out using high-resolution vacuum ultraviolet synchrotron radiation, with quantum chemical calculation...
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MDPI AG
2021-06-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/22/12/6460 |
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| author | Mónica Mendes Fábris Kossoski Ana I. Lozano João Pereira-da-Silva Rodrigo Rodrigues João Ameixa Nykola C. Jones Søren V. Hoffmann Filipe Ferreira da Silva |
| author_facet | Mónica Mendes Fábris Kossoski Ana I. Lozano João Pereira-da-Silva Rodrigo Rodrigues João Ameixa Nykola C. Jones Søren V. Hoffmann Filipe Ferreira da Silva |
| author_sort | Mónica Mendes |
| collection | DOAJ |
| description | We report absolute photoabsorption cross sections for gas-phase 2- and 5-bromopyrimidine in the 3.7–10.8 eV energy range, in a joint theoretical and experimental study. The measurements were carried out using high-resolution vacuum ultraviolet synchrotron radiation, with quantum chemical calculations performed through the nuclear ensemble approach in combination with time-dependent density functional theory, along with additional Franck–Condon Herzberg–Teller calculations for the first absorption band (3.7–4.6 eV). The cross sections of both bromopyrimidines are very similar below 7.3 eV, deviating more substantially from each other at higher energies. In the 7.3–9.0 eV range where the maximum cross-section is found, a single and broad band is observed for 5-bromopyrimidine, while more discernible features appear in the case of 2-bromopyrimidine. Several π* ← π transitions account for the most intense bands, while weaker ones are assigned to transitions involving the nitrogen and bromine lone pairs, the antibonding σ*<sub>Br</sub> orbital, and the lower-lying Rydberg states. A detailed comparison with the available photo-absorption data of bromobenzene is also reported. We have found significant differences regarding the main absorption band, which is more peaked in bromobenzene, becoming broader and shifting to higher energies in both bromopyrimidines. In addition, there is a significant suppression of vibrational structures and of Rydberg states in the pair of isomers, most noticeably for 2-bromopyrimidine. |
| first_indexed | 2024-03-10T10:21:17Z |
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| language | English |
| last_indexed | 2024-03-10T10:21:17Z |
| publishDate | 2021-06-01 |
| publisher | MDPI AG |
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| series | International Journal of Molecular Sciences |
| spelling | doaj.art-3d82cbda5044465b874163ac2201cce72023-11-22T00:24:20ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672021-06-012212646010.3390/ijms22126460Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical CalculationsMónica Mendes0Fábris Kossoski1Ana I. Lozano2João Pereira-da-Silva3Rodrigo Rodrigues4João Ameixa5Nykola C. Jones6Søren V. Hoffmann7Filipe Ferreira da Silva8CEFITEC, Departamento de Física, NOVA School of Science and Technology, FCT NOVA, Universidade NOVA de Lisboa, 2829-516 Caparica, PortugalLaboratoire de Chimie et Physique Quantiques (UMR 5626), Université de Toulouse, CNRS, UPS, CEDEX 09, 31062 Toulouse, FranceCEFITEC, Departamento de Física, NOVA School of Science and Technology, FCT NOVA, Universidade NOVA de Lisboa, 2829-516 Caparica, PortugalCEFITEC, Departamento de Física, NOVA School of Science and Technology, FCT NOVA, Universidade NOVA de Lisboa, 2829-516 Caparica, PortugalCEFITEC, Departamento de Física, NOVA School of Science and Technology, FCT NOVA, Universidade NOVA de Lisboa, 2829-516 Caparica, PortugalCEFITEC, Departamento de Física, NOVA School of Science and Technology, FCT NOVA, Universidade NOVA de Lisboa, 2829-516 Caparica, PortugalISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, DenmarkISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, DenmarkCEFITEC, Departamento de Física, NOVA School of Science and Technology, FCT NOVA, Universidade NOVA de Lisboa, 2829-516 Caparica, PortugalWe report absolute photoabsorption cross sections for gas-phase 2- and 5-bromopyrimidine in the 3.7–10.8 eV energy range, in a joint theoretical and experimental study. The measurements were carried out using high-resolution vacuum ultraviolet synchrotron radiation, with quantum chemical calculations performed through the nuclear ensemble approach in combination with time-dependent density functional theory, along with additional Franck–Condon Herzberg–Teller calculations for the first absorption band (3.7–4.6 eV). The cross sections of both bromopyrimidines are very similar below 7.3 eV, deviating more substantially from each other at higher energies. In the 7.3–9.0 eV range where the maximum cross-section is found, a single and broad band is observed for 5-bromopyrimidine, while more discernible features appear in the case of 2-bromopyrimidine. Several π* ← π transitions account for the most intense bands, while weaker ones are assigned to transitions involving the nitrogen and bromine lone pairs, the antibonding σ*<sub>Br</sub> orbital, and the lower-lying Rydberg states. A detailed comparison with the available photo-absorption data of bromobenzene is also reported. We have found significant differences regarding the main absorption band, which is more peaked in bromobenzene, becoming broader and shifting to higher energies in both bromopyrimidines. In addition, there is a significant suppression of vibrational structures and of Rydberg states in the pair of isomers, most noticeably for 2-bromopyrimidine.https://www.mdpi.com/1422-0067/22/12/6460VUV photoabsorptionhalopyrimidinesvalence and Rydberg statestime-dependent density functional theoryradiosensitizers |
| spellingShingle | Mónica Mendes Fábris Kossoski Ana I. Lozano João Pereira-da-Silva Rodrigo Rodrigues João Ameixa Nykola C. Jones Søren V. Hoffmann Filipe Ferreira da Silva Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical Calculations International Journal of Molecular Sciences VUV photoabsorption halopyrimidines valence and Rydberg states time-dependent density functional theory radiosensitizers |
| title | Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical Calculations |
| title_full | Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical Calculations |
| title_fullStr | Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical Calculations |
| title_full_unstemmed | Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical Calculations |
| title_short | Excited States of Bromopyrimidines Probed by VUV Photoabsorption Spectroscopy and Theoretical Calculations |
| title_sort | excited states of bromopyrimidines probed by vuv photoabsorption spectroscopy and theoretical calculations |
| topic | VUV photoabsorption halopyrimidines valence and Rydberg states time-dependent density functional theory radiosensitizers |
| url | https://www.mdpi.com/1422-0067/22/12/6460 |
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