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Sedmidubská B, Kočišek J. Interaction of low-energy electrons with radiosensitizers. Phys Chem Chem Phys 2024; 26:9112-9136. [PMID: 38376461 DOI: 10.1039/d3cp06003a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
We provide an experimentalist's perspective on the present state-of-the-art in the studies of low-energy electron interactions with common radiosensitizers, including compounds used in combined chemo-radiation therapy and their model systems. Low-energy electrons are important secondary species formed during the interaction of ionizing radiation with matter. Their role in the radiation chemistry of living organisms has become an important topic for more than 20 years. With the increasing number of works and reviews in the field, we would like to focus here on a very narrow area of compounds that have been shown to have radio-sensitizing properties on the one hand, and high reactivity towards low-energy electrons on the other hand. Gas phase experiments studying electron attachment to isolated molecules and environmental effects on reaction dynamics are reviewed for modified DNA components, nitroimidazoles, and organometallics. In the end, we provide a perspective on the future directions that may be important for transferring the fundamental knowledge about the processes induced by low-energy electrons into practice in the field of rational design of agents for concomitant chemo-radiation therapy.
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Affiliation(s)
- Barbora Sedmidubská
- J. Heyrovský Institute of Physical Chemistry of the CAS, Dolejškova 3, 182223 Prague, Czech Republic.
- Department of Nuclear Chemistry, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, 11519 Prague, Czech Republic
- Institut de Chimie Physique, UMR 8000 CNRS and Faculté des sciences d'Orsay, Université Paris Saclay, F-91405 Orsay Cedex, France
| | - Jaroslav Kočišek
- J. Heyrovský Institute of Physical Chemistry of the CAS, Dolejškova 3, 182223 Prague, Czech Republic.
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An S, Kim D, Kim J, Kim SK. Excited-state chemistry of the nitromethane anion mediated by the dipole-bound states revealed by photofragment action spectroscopy. Chem Sci 2023; 14:12231-12237. [PMID: 37969601 PMCID: PMC10631229 DOI: 10.1039/d3sc04342h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 10/12/2023] [Indexed: 11/17/2023] Open
Abstract
We report the first experimental observation of the excited dipole-bound state (DBS) of the cryogenically cooled nitromethane anion (CH3NO2-), where the excess electron is loosely attached to the singlet or triplet neutral-core. Photofragment and photodetachment action spectra have been employed for the dynamic exploration of Feshbach resonances located even far above the electron detachment threshold, giving excitation profiles from the ground anionic state (D0) to the DBSs which match quite well with the spectral structures of the photoelectron spectra. This indicates that the electron transfer from the nonvalence orbital (of DBS) to the valence orbital (of anion) is mainly responsible for the anionic fragmentation channels, giving strong evidence for that the DBS plays a dynamic doorway-role in the anionic fragmentation reactions. Photofragment action spectra have also been obtained for the anionic clusters of (CH3NO2)2-, (CH3NO2)3-, or (CH3NO2·H2O)-, giving the relative yields of various fragments as a function of the excitation energy for each cluster. The absorption profiles of the anionic clusters exhibit substantial blue-shifts compared to the bare nitromethane anion as their ground states are much stabilized by solvation. The anionic fragmentation pattern varies among different clusters, giving essential clues for the thorough understanding of the whole anionic dynamics such as the dynamic role of the short-lived nonvalence-bound states of the clusters.
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Affiliation(s)
- Sejun An
- Department of Chemistry, KAIST Daejeon 34141 Republic of Korea
| | - Dabin Kim
- Department of Chemistry, KAIST Daejeon 34141 Republic of Korea
| | - Junggil Kim
- Department of Chemistry, KAIST Daejeon 34141 Republic of Korea
| | - Sang Kyu Kim
- Department of Chemistry, KAIST Daejeon 34141 Republic of Korea
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Zhang YR, Yuan DF, Wang LS. Probing Dipole-Bound States Using Photodetachment Spectroscopy and Resonant Photoelectron Imaging of Cryogenically Cooled Anions. J Phys Chem Lett 2023; 14:7368-7381. [PMID: 37565830 DOI: 10.1021/acs.jpclett.3c01994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/12/2023]
Abstract
Molecular anions with polar neutral cores can support highly diffuse dipole-bound states below their detachment thresholds due to the long-range charge-dipole interaction. Such nonvalence states constitute a special class of excited electronic states for anions and were observed in early photodetachment experiments to measure the electron affinities of organic radicals. Recent experimental advances, in particular, the ability to create cold anions using a cryogenically cooled Paul trap, have allowed the investigation of dipole-bound excited states at a new level. For the first time, the zero-point level of dipole-bound excited states can be observed via resonant two-photon detachment, and resonant photoelectron spectroscopy can be performed via the above-threshold vibrational levels (Feshbach resonances) of the dipole-bound states. This Perspective describes recent progress in the investigation of dipole-bound states in the authors' lab using an electrospray photoelectron spectroscopy apparatus equipped with a cryogenically cooled Paul trap and high-resolution photoelectron imaging.
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Affiliation(s)
- Yue-Rou Zhang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Dao-Fu Yuan
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
- Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Lai-Sheng Wang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
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Yuan DF, Liu Y, Zhang YR, Wang LS. Observation of a Polarization-Assisted Dipole-Bound State. J Am Chem Soc 2023; 145:5512-5522. [PMID: 36809761 DOI: 10.1021/jacs.3c00246] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
The critical dipole moment to bind an electron was empirically determined to be 2.5 debye, even though smaller values were predicted theoretically. Herein, we report the first observation of a polarization-assisted dipole-bound state (DBS) for a molecule with a dipole moment below 2.5 debye. Photoelectron and photodetachment spectroscopies are conducted for cryogenically cooled indolide anions, where the neutral indolyl radical has a dipole moment of 2.4 debye. The photodetachment experiment reveals a DBS only 6 cm-1 below the detachment threshold along with sharp vibrational Feshbach resonances. Rotational profiles are observed for all of the Feshbach resonances, which are found to have surprisingly narrow linewidths and long autodetachment lifetimes attributed to weak coupling between vibrational motions and the nearly free dipole-bound electron. Calculations suggest that the observed DBS has π-symmetry stabilized by the strong anisotropic polarizability of indolyl.
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Affiliation(s)
- Dao-Fu Yuan
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Yuan Liu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Yue-Rou Zhang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Lai-Sheng Wang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
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Ouyang L, Lin H, Zhuang P, Shao Y, Khosravifarsani M, Guérin B, Zheng Y, Sanche L. DNA radiosensitization by terpyridine-platinum: damage induced by 5 and 10 eV transient anions. NANOSCALE 2023; 15:3230-3242. [PMID: 36722902 DOI: 10.1039/d2nr05403e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Chemoradiation therapy (CRT), which combines a chemotherapeutic drug with ionizing radiation (IR), is the most common cancer treatment. At the molecular level, the binding of Pt-drugs to DNA sensitizes cancer cells to IR, mostly by increasing the damage induced by secondary low-energy (0-20 eV) electrons (LEEs). We investigate such enhancements by binding terpyridine-platinum (Tpy-Pt) to supercoiled plasmid DNA. Fifteen nanometer thick films of Tpy-Pt-DNA complexes in a molar ratio of 5 : 1 were irradiated with monoenergetic electrons of 5 and 10 eV, which principally attach to the DNA bases to form transient anions (TAs) decaying into a multitude of bond-breaking channels. At both energies, the effective yields of crosslinks (CLs), base damage (BD) related CLs, single and double strand breaks (SSBs and DSBs), non-DSB-cluster lesions, loss of supercoiled configuration and base lesions are 6.5 ± 1.5, 8.8± 3.0, 88 ± 11, 5.3 ± 1.3, 9.6 ± 2.2, 106 ± 17, 189 ± 31 × 10-15 per electron per molecule, and 11.9 ± 2.6, 19.9 ± 4.4, 128 ± 18, 7.7 ± 3.0, 13.4 ± 3.9, 144 ± 19, 229 ± 42 × 10-15 per electron per molecule, respectively. DNA damage increased 1.2-4.2-fold due to Tpy-Pt, the highest being for BD-related CLs. These enhancements are slightly higher than those obtained by the conventional Pt-drugs cisplatin, carboplatin and oxaliplatin, apart from BD-related CLs, which are about 3 times higher. Enhancements are related to the strong perturbation of the DNA helix by Tpy-Pt, its high dipole moment and its favorable binding to guanine (G), all of which increase bond-breaking via TA formation. In CRT, Tpy-Pt could considerably enhance crosslinking within genomic DNA and between DNA and other components of the nucleus, causing roadblocks to replication and transcription, particularly within telomeres, where it binds preferentially within G-quadruplexes.
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Affiliation(s)
- Liangde Ouyang
- State Key Laboratory of Photocatalysis on Energy and Environment, Faculty of Chemistry, Fuzhou University, Fuzhou 350116, P.R. China
| | - Hong Lin
- State Key Laboratory of Photocatalysis on Energy and Environment, Faculty of Chemistry, Fuzhou University, Fuzhou 350116, P.R. China
| | - Puxiang Zhuang
- State Key Laboratory of Photocatalysis on Energy and Environment, Faculty of Chemistry, Fuzhou University, Fuzhou 350116, P.R. China
| | - Yu Shao
- State Key Laboratory of Photocatalysis on Energy and Environment, Faculty of Chemistry, Fuzhou University, Fuzhou 350116, P.R. China
| | - Meysam Khosravifarsani
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada J1H 5N4.
| | - Brigitte Guérin
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada J1H 5N4.
| | - Yi Zheng
- State Key Laboratory of Photocatalysis on Energy and Environment, Faculty of Chemistry, Fuzhou University, Fuzhou 350116, P.R. China
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada J1H 5N4.
| | - Léon Sanche
- Department of Nuclear Medicine and Radiobiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, QC, Canada J1H 5N4.
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Yuan DF, Zhang YR, Wang LS. Dipole-Bound State, Photodetachment Spectroscopy, and Resonant Photoelectron Imaging of Cryogenically-Cooled 2-Cyanopyrrolide. J Phys Chem A 2022; 126:6416-6428. [PMID: 36097646 DOI: 10.1021/acs.jpca.2c04405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Valence-bound anions with polar neutral cores can have diffuse dipole-bound excited states just below the electron detachment threshold. Because of the similarity in geometry and vibrational frequencies between the dipole-bound states (DBSs) and the corresponding neutrals, DBSs have been exploited as intermediate states to conduct resonant photoelectron spectroscopy (PES), resulting in highly non-Franck-Condon photoelectron spectra via vibrational autodetachment and providing much richer vibrational information than conventional PES. Here, we report a photodetachment and high-resolution photoelectron imaging study of the 2-cyanopyrrolide anion, cooled in a cryogenic ion trap. The electron affinity of the 2-cyanopyrrolyl radical is measured to be 3.0981 ± 0.0006 eV (24 988 ± 5 cm-1). A DBS is observed for 2-cyanopyrrolide at 240 cm-1 below its detachment threshold using photodetachment spectroscopy. Twenty-three above-threshold vibrational resonances (Feshbach resonances) of the DBS are observed. Resonant PES is conducted at each Feshbach resonance, yielding a wealth of vibrational information about the 2-cyanopyrrolyl radical. Resonant two-photon PES confirms the s-like dipole-bound orbital and reveals a relatively long lifetime of the bound zero-point level of the DBS. Fundamental frequencies for 19 vibrational modes (out of a total of 24) are obtained for the cyanopyrrolyl radical, including six out-of-plane modes. The current work provides important spectroscopic information about 2-cyanopyrrolyl, which should be valuable for the study of this radical in combustion or astronomical environments.
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Affiliation(s)
- Dao-Fu Yuan
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Yue-Rou Zhang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Lai-Sheng Wang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
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Zhang YR, Yuan DF, Wang LS. Probing the Strong Nonadiabatic Interactions in the Triazolyl Radical Using Photodetachment Spectroscopy and Resonant Photoelectron Imaging of Cryogenically Cooled Anions. J Am Chem Soc 2022; 144:16620-16630. [PMID: 36048511 DOI: 10.1021/jacs.2c07167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Although the adiabatic potential energy surfaces defined by the Born-Oppenheimer approximation are the cornerstones for understanding the electronic structure and spectroscopy of molecular systems, nonadiabatic effects due to the coupling of electronic states by nuclear motions are common in complex molecular systems. The nonadiabatic effects were so strong in the 1,2,3-triazolyl radical (C2H2N3) that the photoelectron spectrum of the triazolide anion was rendered unassignable and could only be understood using nonadiabatic calculations, involving the four low-lying electronic states of triazolyl. Using photodetachment spectroscopy and resonant photoelectron imaging of cryogenically cooled anions, we are able to completely unravel the complex vibronic levels of the triazolyl radical. Photodetachment spectroscopy reveals a dipole-bound state for the triazolide anion at 172 cm-1 below the detachment threshold and 32 vibrational Feshbach resonances. Resonant photoelectron imaging is conducted by tuning the detachment laser to each of the Feshbach resonances. Combining the photodetachment spectrum and the resonant photoelectron spectra, we are able to assign all 28 vibronic peaks resolved for the triazolyl radical. Fundamental frequencies for 12 vibrational modes of the ground state of the triazolyl radical are measured experimentally. The current study provides unprecedented experimental vibronic information, which will be valuable to verify theoretical models to treat nonadiabatic effects involving multiple electronic states.
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Affiliation(s)
- Yue-Rou Zhang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Dao-Fu Yuan
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Lai-Sheng Wang
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
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