Mendes M, Probst M, Maihom T, García G, Limão-Vieira P
Atomic and Molecular Collisions Laboratory, CEFITEC, Department of Physics , Universidade NOVA de Lisboa , Campus de Caparica , 2829-516 Caparica , Portugal.
Instituto de Física Fundamental , Consejo Superior de Investigaciones Científicas , Serrano 113-bis , 28006 Madrid , Spain.
J Phys Chem A. 2019 May 9;123(18):4068-4073. doi: 10.1021/acs.jpca.9b02064. Epub 2019 Apr 30.
We have performed comprehensive charge-transfer experiments yielding negative ion formation in collisions of fast neutral potassium atoms with nitroimidazole and methylated derivative molecules. The anionic pattern reveals that in the unimolecular decomposition of the precursor parent anion, single and multiple bond cleavages are attained. Selective excision of hydrogen atoms from the N1 position in 4-nitroimidazole (4NI) is completely blocked upon methylation in 1-methyl-4-nitroimidazole (1m4NI) and 1-methyl-5-nitroimidazole (1m5NI). Additionally, only 4NI and 2-nitroimidazole (2NI) are efficient in selectively producing neutral OH and NO radicals in contrast to 1m4NI and 1m5NI. These findings present a novel experimental evidence of selective chemical bond breaking by just tuning the proper collision energy in atom-molecule collision experiments. The present work contributes to the current need of pinpointing a class of charge-transfer collisions that exhibit selective reactivity of the kind demonstrated here, extending to tailored chemical control for different applications such as tumor radiation therapy through nitroimidazole-based radiosensitization.
我们进行了全面的电荷转移实验，该实验在快速中性钾原子与硝基咪唑及甲基化衍生物分子的碰撞中产生负离子形成。阴离子模式表明，在前体母阴离子的单分子分解中，实现了单键和多键断裂。在1-甲基-4-硝基咪唑（1m4NI）和1-甲基-5-硝基咪唑（1m5NI）中甲基化后，4-硝基咪唑（4NI）中N1位置的氢原子选择性切除被完全阻断。此外，与1m4NI和1m5NI相比，只有4NI和2-硝基咪唑（2NI）能有效地选择性产生中性OH和NO自由基。这些发现为通过在原子-分子碰撞实验中调整适当的碰撞能量来选择性地断裂化学键提供了新的实验证据。目前的工作满足了当前确定一类电荷转移碰撞的需求，这类碰撞表现出此处所展示的那种选择性反应性，扩展到了针对不同应用的定制化学控制，如通过基于硝基咪唑的放射增敏进行肿瘤放射治疗。
