Tsuge Masashi, Chen Yu-Hsuan, Lee Yuan-Pern
Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 300093, Taiwan.
Institute of Low Temperature Sciences, Hokkaido University, Sapporo 060-0819, Japan.
J Phys Chem A. 2020 Sep 17;124(37):7500-7510. doi: 10.1021/acs.jpca.0c06079. Epub 2020 Sep 1.
The isomers of monohydrogenated aniline (HCHNH) are regarded as important intermediates in reduction reactions of aniline, but their spectral identification has been limited to electron paramagnetic resonance in an adamantane matrix. We report here infrared (IR) spectra of two least-energy isomers of HCHNH, produced on electron bombardment during the deposition of a matrix of aniline and -hydrogen at 3.2 K. The intensities of IR lines of HCHNH increased during maintenance of the electron-bombarded matrix in darkness for a prolonged period because of the neutralization of protonated aniline, HCHNH, by trapped electrons and further reactions between aniline and the unreacted hydrogen atoms that were produced during electron bombardment. The observed lines were grouped according to their behaviors on secondary photolysis with light at 520, 465, and 375 nm. On comparison of experimental spectra with quantum chemically predicted spectra for four possible isomers of HCHNH, lines in one group were assigned to the most stable -HCHNH and those in the other group were assigned to the secondmost stable -HCHNH. Their photolytic behaviors at varied wavelengths are consistent with predicted ultraviolet absorption bands. The mechanisms of formation of these isomers are discussed according to semiquantitative analysis.
单氢化苯胺（HCHNH）的异构体被视为苯胺还原反应中的重要中间体，但其光谱鉴定仅限于在金刚烷基质中的电子顺磁共振。我们在此报告了在3.2 K下沉积苯胺和氢气基质期间电子轰击产生的HCHNH的两种能量最低异构体的红外（IR）光谱。由于质子化苯胺HCHNH被捕获电子中和，以及苯胺与电子轰击期间产生的未反应氢原子之间的进一步反应，在黑暗中长时间维持电子轰击基质时，HCHNH的IR线强度增加。观察到的谱线根据它们在520、465和375 nm光二次光解时的行为进行分组。将实验光谱与HCHNH四种可能异构体的量子化学预测光谱进行比较时，一组谱线被指定为最稳定的-HCHNH，另一组谱线被指定为第二稳定的-HCHNH。它们在不同波长下的光解行为与预测的紫外吸收带一致。根据半定量分析讨论了这些异构体的形成机制。
