McGee Conor J, McGinnis Kristen Rose, Jarrold Caroline Chick
Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States.
J Phys Chem A. 2023 Oct 19;127(41):8556-8565. doi: 10.1021/acs.jpca.3c04016. Epub 2023 Oct 10.
Substituents have a profound effect on the electronic structure of the benzene molecule. In this paper, we present new photoelectron spectra of the CHF molecular anion, to test predictions [ 2017, 188, e25504] that pentafluorobenzene has a positive electron affinity, as hexafluorobenzene was already known to have. The PE spectrum of CHF exhibits a broad and vibrationally unresolved band due to significant differences between the structure of the anion and the neutral. The vertical detachment energy (VDE) of CHF is determined to be 1.33 ± 0.05 eV, and the lowest binding energy at which the signal is observed is 0.53 ± 0.05 eV, which, if taken as the electron affinity, is in good agreement with the computed value. In addition, we attempted to generate intact CHF molecular ions using the 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, and 1,2,4,5-tetrafluorobenzene precursors, as tetrafluorobenzene was predicted to have a near-zero but marginally positive electron affinity. Using a photoemission anion source, we were not able to produce the intact tetrafluorobenzene anion. Density functional theory calculations support a more detailed discussion of the impact of fluorine substitution on the electronic structure of these species.
取代基对苯分子的电子结构有深远影响。在本文中，我们展示了CHF分子阴离子的新光电子能谱，以检验[2017, 188, e25504]中关于五氟苯具有正电子亲和势的预测，因为已知六氟苯具有正电子亲和势。由于阴离子和中性分子结构存在显著差异，CHF的光电子能谱呈现出一个宽的、振动未分辨的谱带。CHF的垂直脱附能（VDE）被确定为1.33±0.05电子伏特，观察到信号的最低结合能为0.53±0.05电子伏特，若将此作为电子亲和势，则与计算值吻合良好。此外，我们尝试使用1,2,3,4 - 四氟苯、1,2,3,5 - 四氟苯和1,2,4,5 - 四氟苯前体生成完整的CHF分子离子，因为预测四氟苯具有接近零但略微为正的电子亲和势。使用光发射阴离子源，我们未能产生完整的四氟苯阴离子。密度泛函理论计算支持对氟取代对这些物种电子结构影响的更详细讨论。
