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Updated: Nov 10, 2025
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NMR-Based Fragment Screening in a Minimum Sample but Maximum Automation Mode
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Ring-Selective Fragmentation in the Tirapazamine Molecule upon Low-Energy Electron Attachment
Eugene Arthur-Baidoo1,2, Joao Ameixa1,2,3, Milan Ončák1
1Institute for Ion Physics and Applied Physics, University of Innsbruck, Technikerstrasse 25/3, 6020 Innsbruck, Austria.
International Journal of Molecular Sciences
|April 3, 2021
Summary
Dissociative electron attachment to tirapazamine involves electron attachment and anion excitation. A key step is OH radical predissociation, leading to triazine ring destabilization and nitrogenous fragment release.
Area of Science:
- Chemical Physics
- Quantum Chemistry
Background:
- Tirapazamine is a bioreductive drug with potential anticancer properties.
- Understanding its electron interaction mechanisms is crucial for its application.
Purpose of the Study:
- To elucidate the mechanism of dissociative electron attachment to tirapazamine.
- To identify the primary dissociation pathways and resulting fragments.
Main Methods:
- Crossed electron-molecule beam experiments were conducted.
- Quantum chemical calculations were employed to model the process.
Main Results:
- Electron attachment leads to an excited anion state (D1).
- A rapid transition to the ground state occurs via a conical intersection.
- OH radical predissociation, potentially with roaming, initiates heavier ion formation.
- The triazine ring destabilizes, releasing nitrogenous species; the benzene ring remains intact.
- Small anionic fragment origins are unclear but do not involve benzene ring cleavage.
Conclusions:
- The study proposes a detailed mechanism for tirapazamine dissociative electron attachment.
- OH radical predissociation is identified as a critical initial step for major fragment formation.
- The stability of the benzene ring during the process is confirmed.
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