Department of Earth and Environmental Science and Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6243, United States.
Solar System Department, Andalusian Institute for Astrophysics, Consejo Superior de Investigaciones Científicas, Granada 18008, Spain.
J Am Chem Soc. 2020 Jul 15;142(28):12467-12477. doi: 10.1021/jacs.0c05232. Epub 2020 Jul 3.
Iodine is enriched in marine aerosols, particularly in coastal mid-latitude atmospheric environments, where it initiates the formation of new aerosol particles with iodic acid (HIO) composition. However, particle formation in polluted and semipolluted locations is inhibited when the iodine monoxide radical (IO) is intercepted by NO to form the iodine nitrate (IONO). The primary fate of IONO is believed to be, besides photolysis, uptake by aerosol surfaces, leading to particulate iodine activation. Herein we have performed Born-Oppenheimer molecular dynamics (BOMD) simulations and gas-phase quantum chemical calculations to study the iodine acids-iodine nitrate [HIO ( = 2 and 3)-IONO] dynamics at the air-water interface modeled by a water droplet of 191 water molecules. The results indicate that IONO does not react directly with these iodine acids, but forms an unusual kind of interaction with them within a few picoseconds, which is characterized as halogen bonding. The halogen bond-driven HIO-IONO complex at the air-water interface undergoes deprotonation and exists as IO-IONO anion, whereas the HIO-IONO complex does not exhibit any proton loss to the interfacial water molecules. The gas-phase quantum chemical calculations suggest that the HIO-IONO and HIO-IONO complexes have appreciable stabilization energies, which are significantly enhanced upon deprotonation of iodine acids, indicating that these halogen bonds are fairly stable. These IONO-induced halogen bonds explain the rapid loss of IONO to background aerosol. Moreover, they appear to work against iodide formation. Thus, they may play an important role in enhancing the amount of atmospherically nonrecyclable iodine (iodate) in marine aerosol.
碘在海洋气溶胶中很丰富，特别是在沿海中纬度大气环境中，在那里它会引发碘酸（HIO）组成的新气溶胶颗粒的形成。然而，当碘一氧化物自由基（IO）被 NO 拦截形成碘硝酸盐（IONO）时，污染和半污染地区的颗粒形成会受到抑制。IONO 的主要命运除了光解外，还被气溶胶表面吸收，导致颗粒碘的活化。在此，我们通过 Born-Oppenheimer 分子动力学（BOMD）模拟和气相量子化学计算，研究了在由 191 个水分子组成的水滴模型中，碘酸-碘硝酸盐[HIO（=2 和 3）-IONO]在气-液界面上的动力学。结果表明，IONO 不会直接与这些碘酸反应，但在几皮秒内与它们形成一种不寻常的相互作用，其特征为卤素键。气-液界面上的卤素键驱动的 HIO-IONO 配合物经历去质子化，以 IO-IONO 阴离子形式存在，而 HIO-IONO 配合物不会向界面水分子失去任何质子。气相量子化学计算表明，HIO-IONO 和 HIO-IONO 配合物具有相当大的稳定能，在碘酸去质子化后显著增强，表明这些卤素键相当稳定。这些由 IONO 诱导的卤素键解释了 IONO 快速向背景气溶胶的损失。此外，它们似乎对形成碘化物不利。因此，它们可能在增强海洋气溶胶中大气不可回收碘（碘酸盐）的含量方面发挥重要作用。
