Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal.
Département de Physique, LPMC, Faculté des Sciences de Tunis, Université de Tunis el Manar, Tunis 2092, Tunisia.
Molecules. 2022 Jun 28;27(13):4134. doi: 10.3390/molecules27134134.
This novel work reports nimorazole (NIMO) radiosensitizer reduction upon electron transfer in collisions with neutral potassium (K) atoms in the lab frame energy range of 10-400 eV. The negative ions formed in this energy range were time-of-flight mass analyzed and branching ratios were obtained. Assignment of different anions showed that more than 80% was due to the formation of the non-dissociated parent anion NIMO at 226 u and nitrogen dioxide anion NO at 46 u. The rich fragmentation pattern revealed that significant collision induced the decomposition of the 4-nitroimidazole ring, as well as other complex internal reactions within the temporary negative ion formed after electron transfer to neutral NIMO. Other fragment anions were only responsible for less than 20% of the total ion yield. Additional information on the electronic state spectroscopy of nimorazole was obtained by recording a K energy loss spectrum in the forward scattering direction ( ≈ 0°), allowing us to determine the most accessible electronic states within the temporary negative ion. Quantum chemical calculations on the electronic structure of NIMO in the presence of a potassium atom were performed to help assign the most significant lowest unoccupied molecular orbitals participating in the collision process. Electron transfer was shown to be a relevant process for nimorazole radiosensitisation through efficient and prevalent non-dissociated parent anion formation.
这项新工作报道了在实验室框架能量范围内为 10-400 eV 时，与中性钾（K）原子碰撞中电子转移时尼莫唑（NIMO）增敏剂的减少。在这个能量范围内形成的负离子通过飞行时间质谱进行了分析，并获得了分支比。不同阴离子的分配表明，超过 80%归因于在 226 u 处形成非离解母体阴离子 NIMO 和在 46 u 处形成二氧化氮阴离子 NO。丰富的碎裂模式表明，在电子转移到中性 NIMO 后形成的临时负离子内，显著的碰撞会导致 4-硝基咪唑环的分解以及其他复杂的内部反应。其他碎片阴离子仅占总离子产额的不到 20%。通过记录前向散射方向（≈0°）的 K 能量损失谱，获得了关于尼莫唑电子态光谱的更多信息，这使我们能够确定临时负离子内最易接近的电子态。在存在钾原子的情况下对 NIMO 的电子结构进行了量子化学计算，以帮助分配参与碰撞过程的最重要的最低未占分子轨道。电子转移被证明是通过有效和普遍的非离解母体阴离子形成来实现尼莫唑增敏的相关过程。
