3 years ago

Isomer Selectivity in Low-Energy Electron Attachment to Nitroimidazoles

Isomer Selectivity in Low-Energy Electron Attachment to Nitroimidazoles
Katharina Fink, Stephan Denifl, Linda Feketeová, Stefan E. Huber, Anita Ribar, Michael Probst
Low-energy electrons effectively decompose the isomers 2-nitroimidazole and 4(5)-nitroimidazole by dissociative electron attachment (DEA) into a variety of fragment anions and radicals. The present study shows that a distinct selectivity for the two isomers occurs in the DEA reactions. Several new decay channels are observed for 2-nitroimidazole, including a dominant one leading to the loss of molecular H2O by attachment of a low-energy electron. In contrast, the loss of a single hydrogen atom is a much more efficient reaction in DEA to 4(5)-nitroimidazole. Quantum chemical calculations were carried out to explain the pronounced isomer effect found in the DEA experiment. Although the free energies of the reactions are similar for the different isomers, the very different natures of the dipole-bound states and valence-bound anions lead to preference for or hindrance of a particular dissociation channel. Nitroimidazolic compounds are considered as radiosensitizing compounds in tumor radiation therapy. The enhanced formation of fragments, including the highly reactive hydroxyl radical, in DEA to 2-nitroimidazole suggests that it may be a more efficient radiosensitizing agent than 4(5)-nitroimidazoles. Selective attachment: Low-energy electrons, which play an important role in the induction of radiation damage, decompose 2-nitroimidazole (2NI) by dissociative electron attachment (DEA) into variety of radicals more efficiently than its isomers 4NI and 5NI. Several new decay channels were observed, including a dominant channel leading to the loss of molecular H2O. Enhanced formation of fragments, including the highly reactive hydroxyl radical, in DEA to 2NI suggests that it may be a more efficient radiosensitizing agent than 4(5)-nitroimidazoles (see figure).

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201702644

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