Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria.
Center for Molecular Biosciences Innsbruck, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria.
Int J Mol Sci. 2022 Jul 28;23(15):8325. doi: 10.3390/ijms23158325.
We investigate dissociative electron attachment to 5-fluorouracil (5-FU) employing a crossed electron-molecular beam experiment and quantum chemical calculations. Upon the formation of the 5-FU anion, 12 different fragmentation products are observed, the most probable dissociation channel being H loss. The parent anion, 5-FU, is not stable on the experimental timescale (~140 µs), most probably due to the low electron affinity of FU; simple HF loss and F formation are seen only with a rather weak abundance. The initial dynamics upon electron attachment seems to be governed by hydrogen atom pre-dissociation followed by either its full dissociation or roaming in the vicinity of the molecule, recombining eventually into the HF molecule. When the HF molecule is formed, the released energy might be used for various ring cleavage reactions. Our results show that higher yields of the fluorine anion are most probably prevented through both faster dissociation of an H atom and recombination of F with a proton to form HF. Resonance calculations indicate that F is formed upon shape as well as core-excited resonances.
我们采用交叉电子-分子束实验和量子化学计算研究了 5-氟尿嘧啶（5-FU）的电子离解。在 5-FU 阴离子的形成过程中，观察到 12 种不同的碎片产物，最可能的解离通道是 H 损失。母体阴离子 5-FU 在实验时间尺度上（约 140µs）不稳定，最可能是由于 FU 的低电子亲和力；只有在相当弱的丰度下才会看到简单的 HF 损失和 F 形成。电子附加后的初始动力学似乎由氢原子预离解控制，然后是其完全离解或在分子附近漫游，最终重新组合成 HF 分子。当 HF 分子形成时，释放的能量可能用于各种环裂解反应。我们的结果表明，通过更快地离解 H 原子和 F 与质子重新组合形成 HF，可能会阻止氟阴离子的更高产率。共振计算表明 F 是通过形状以及芯激发共振形成的。
