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Вокин, А. И.; Sherstyannikova, L. V.; Krivoruchka, I. G.; Aksamentova, T. N.; Krylova, O. V.; Turchaninov, V. K.

doi:10.1023/a:1026325523361

Cited by 11 publications

(10 citation statements)

References 13 publications

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“…This fit of the experimental data with a ratio of populations of 1:0.70 for 4NI/5NI shows that both tautomers are present in the gas-phase with a slightly higher population of the 4NI tautomer. It corresponds to a difference in free energy of only 1.1 kJ/mol at 390 K. This finding finally clarifies the ambiguity raised in the gas-phase experiments on tautomeric 4(5)-nitroimidazole, ,, regarding which tautomer is dominant, and contradicts the conclusion of Jimenez et al, although we note that the temperature of 4(5)-nitroimidazole in their study was not reported. Therefore, it would be of interest to investigate the ratio of population of 4NI and 5NI at different temperatures.…”

Section: Resultssupporting

confidence: 61%

Photoelectron Spectra and Electronic Structures of the Radiosensitizer Nimorazole and Related Compounds

et al. 2015

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Soft X-ray photoelectron spectroscopy has been used to investigate the radiosensitizer nimorazole and related model compounds. We report the valence and C, N, and O 1s photoemission spectra and K-edge NEXAFS spectra of gas-phase nimorazole, 1-methyl-5-nitroimidazole, and 4(5)-nitroimidazole in combination with theoretical calculations. The valence band and core level spectra are in agreement with theory. We determine the equilibrium populations of the two tautomers in 4(5)-nitroimidazole and find a ratio of 1:0.7 at 390 K. The NEXAFS spectra of the studied nitroimidazoles show excellent agreement with spectra of compounds available in the literature that exhibit a similar chemical environment. By comparing 1-methyl-5-nitroimidazole (single tautomer) with 4(5)-nitroimidazole, we are able to disentangle the photoemission and photoabsorption spectra and identify features due to each single tautomer.

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Section: Resultssupporting

confidence: 61%

Photoelectron Spectra and Electronic Structures of the Radiosensitizer Nimorazole and Related Compounds

et al. 2015

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“…The tautomeric equilibrium favors 4-nitroimidazole in the crystal structure. 5-Nitroimidazole is most stable in the gas phase, 17 however, both tautomers have been recently observed in the gas phase at nearly equal levels. 18 N-protonation or deprotonation of 4-nitroimidazole and 5-nitroimidazole leads to the formation of identical [M+H] + and [M-H] À , respectively (Fig.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Decomposition of nitroimidazole ions: experiment and theory

Feketeová

Postler

Zavras

et al. 2015

Phys. Chem. Chem. Phys.

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Nitroimidazoles are important compounds with chemotherapeutic applications as antibacterial drugs or as radiosensitizers in radiotherapy. Despite their use in biological applications, little is known about the fundamental properties of these compounds. Understanding the ionization reactions of these compounds is crucial in evaluating the radiosensitization potential and in developing new and more effective drugs. Thus, the present study investigates the decomposition of negative and positive ions of 2-nitroimidazole and 4(5)-nitroimidazole using low- and high-energy Collision-Induced Dissociation (CID) and Electron-Induced Dissociation (EID) by two different mass spectrometry techniques and is supported by quantum chemistry calculations. EID of [M+H](+) leads to more extensive fragmentation than CID and involves many radical cleavages including loss of H˙ leading to the formation of the radical cation, M˙(+). The stability (metastable decay) and the fragmentation (high-energy CID) of the radical cation M˙(+) have been probed in a crossed-beam experiment involving primary electron ionization of the neutral nitroimidazole. Thus, fragments in the EID spectra of [M+H](+) that come from further dissociation of radical cation M˙(+) have been highlighted. The loss of NO˙ radical from M˙(+) is associated with a high Kinetic Energy Release (KER) of 0.98 eV. EID of [M-H](-) also leads to additional fragments compared to CID, however, with much lower cross section. Only EID of [M+H](+) leads to a slight difference in the decomposition of 2-nitroimidazole and 4(5)-nitroimidazole.

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“…The 4-nitroimidazole (4NI) and 5-nitroimidazole (5NI) are regioisomers that differ in the position of the H atom on either of the two N atoms within the imidazole ring (see inset in Figure 1) and are almost degenerate in energy. The 4NI isomer was found to be more stable than 5NI in water 18 and in the crystalline state, 19 while in the gas phase they coexist in a tautomeric equilibrium. 18 XPS measurements together with density functional theory (DFT) based theoretical calculations by Feketeovà et al 20 found a relative population of 1:0.7 for the 4NI:5NI molecules at 117 • C. Therefore, in the following, we will refer to the 4(5)NI sample assuming that both isomers coexist in gas phase experiments.…”

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confidence: 96%

Communication: “Position” does matter: The photofragmentation of the nitroimidazole isomers

Bolognesi

Casavola

Cartoni

et al. 2016

The Journal of Chemical Physics

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A combined experimental and theoretical approach has been used to disentangle the fundamental mechanisms of the fragmentation of the three isomers of nitroimidazole induced by vacuum ultra-violet (VUV) radiation, namely, 4-, 5-, and 2-nitroimidazole. The results of mass spectrometry as well as photoelectron–photoion coincidence spectroscopy display striking differences in the radiation-induced decomposition of the different nitroimidazole radical cations. Based on density functional theory (DFT) calculations, a model is proposed which fully explains such differences, and reveals the subtle fragmentation mechanisms leading to the release of neutral species like NO, CO, and HCN. Such species have a profound impact in biological media and may play a fundamental role in radiosensitising mechanisms during radiotherapy.

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Untitled

Cited by 11 publications

References 13 publications

Photoelectron Spectra and Electronic Structures of the Radiosensitizer Nimorazole and Related Compounds

Photoelectron Spectra and Electronic Structures of the Radiosensitizer Nimorazole and Related Compounds

Decomposition of nitroimidazole ions: experiment and theory

Communication: “Position” does matter: The photofragmentation of the nitroimidazole isomers

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