Li Xiaolong, Fan Wenbin, Wang Lina, Jiang Junjie, Du Yanqi, Fang Wei, Trabelsi Tarek, Francisco Joseph S, Yang Jiawei, Li Jun, Zhou Mingfei, Zeng Xiaoqing
Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, China.
Department of Earth and Environment Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6243, United States.
J Am Chem Soc. 2024 Jul 24;146(29):20494-20499. doi: 10.1021/jacs.4c06851. Epub 2024 Jul 13.
The photochemistry of nitrous acid (HONO), encompassing dissociation into OH and NO as well as the reverse association reaction, plays a pivotal role in atmospheric chemistry. Here, we report the direct observation of nitrosyl--hydroxide (HOON) in the photochemistry of HONO, employing matrix-isolation IR and UV-vis spectroscopy. Despite a barrier of approximately 30 kJ/mol, HOON undergoes spontaneous rearrangement to the more stable HONO isomer through quantum mechanical tunneling, with a half-life of 28 min at 4 K. Kinetic isotope effects and instanton theory calculations reveal that the tunneling process involves the concerted motion of the NO moiety (65.2%) and the hydrogen atom (32.3%). Our findings underscore the significance of HOON as a key intermediate in the photolytic dissociation-association cycle of HONO at low temperatures.
亚硝酸（HONO）的光化学，包括分解为OH和NO以及逆向缔合反应，在大气化学中起着关键作用。在此，我们报告了利用基质隔离红外光谱和紫外可见光谱对HONO光化学过程中亚硝酰氢氧化物（HOON）的直接观测。尽管存在约30 kJ/mol的势垒，但HOON通过量子力学隧穿自发重排为更稳定的HONO异构体，在4 K时半衰期为28分钟。动力学同位素效应和瞬子理论计算表明，隧穿过程涉及NO部分（65.2%）和氢原子（32.3%）的协同运动。我们的研究结果强调了HOON作为低温下HONO光解-缔合循环中关键中间体的重要性。
