Lee Han Myoung, Kolaski Maciej, Kim Kwang S
Department of Chemistry, Center for Superfunctional Materials and Center for Basic Sciences, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang, 790-784, Korea.
Chemphyschem. 2008 Mar 14;9(4):567-71. doi: 10.1002/cphc.200700771.
Using high-level ab initio calculations and excited state ab initio molecular dynamics simulations, we show that hydrated iodic acids release hydrogen radicals and/or hydrogen molecules as well as iodine radicals upon excitation. Its photoreaction process involving charge transfer to the solvent takes place in four steps: 1) hydration of the acid, 2) charge transfer to water upon excitation of hydrated acid, 3) detachment of the neutral iodine atom, and 4) detachment of the hydrogen radical. The iodine detachment process from excited hydrated hydro-iodic acids is exothermic and the detachment of hydrogen radicals from hydrated hydronium radicals is spontaneous if the initial kinetic energy of the cluster is high enough to get over the activation barrier of the detachment. The complete release of the radicals can be understood in terms of kinetics. This study shows how the hydrogen and halogen radicals are dissociated and released from their hydrated acids. Simple experiments corroborate our predicted mechanism for the release of hydrogen molecules from iodic acid in water by ultraviolet light.
通过高水平的从头算计算和激发态从头算分子动力学模拟，我们表明水合碘酸在激发时会释放氢自由基和/或氢分子以及碘自由基。其涉及向溶剂电荷转移的光反应过程分四个步骤进行：1）酸的水合作用；2）水合酸激发时向水的电荷转移；3）中性碘原子的脱离；4）氢自由基的脱离。如果团簇的初始动能足够高以克服脱离的活化能垒，那么从激发的水合氢碘酸中碘的脱离过程是放热的，并且从水合水合氢离子自由基中氢自由基的脱离是自发的。自由基的完全释放可以从动力学角度来理解。这项研究展示了氢和卤素自由基如何从它们的水合酸中解离和释放出来。简单的实验证实了我们所预测的碘酸在水中通过紫外光释放氢分子的机制。
