Zilberg Shmuel, Mizrahi Amir, Meyerstein Dan, Kornweitz Haya
Chemical Sciences Department, Ariel University, Ariel, Israel.
Chemistry Department, Ben-Gurion University, Beer-Sheva, Israel.
Phys Chem Chem Phys. 2018 Apr 4;20(14):9429-9435. doi: 10.1039/C7CP08240A.
An effort to reproduce the chemical and physical properties of carbonate and carbonate anion radicals in aqueous solutions by DFT proves that one has to include an inner hydration sphere of six water molecules for both anions. Application of the SMD model to CO3(H2O)62- and CO3(H2O)6˙- enables achievement of the experimental value of the redox potential of the CO3(H2O)6˙-/2- couple. This is a result of the direct inclusion of a considerable charge transfer (CT) from CO32- to its inner hydration sphere in the calculation of the hydration effect. The HOMO of clusters is an analogue of the non-bonding σ-type a2'-HOMO of the parent CO3 moiety with a σ*(OH) contribution. This is a MO manifestation of the CT to the first hydration shell. The localization of the CT on the first hydration shell also re-produces the very strong OHO stretch peak. Furthermore, the very large difference in the hydration energies of CO32- and CO3˙- which causes the very large differences in the length of the C-OH-O hydrogen bonds suggests that the oxidations by CO3˙- proceed via the inner sphere mechanism.
通过密度泛函理论（DFT）来重现水溶液中碳酸根和碳酸根阴离子自由基的化学和物理性质的研究表明，对于这两种阴离子，都必须包含一个由六个水分子组成的内水化层。将SMD模型应用于CO3(H2O)62-和CO3(H2O)6˙-，能够得到CO3(H2O)6˙-/2-电对氧化还原电位的实验值。这是因为在计算水化效应时直接纳入了从CO32-到其内部水化层的大量电荷转移（CT）。团簇的最高占据分子轨道（HOMO）类似于母体CO3部分的非键σ型a2'-HOMO，并带有σ*(OH)贡献。这是电荷转移到第一水化层的分子轨道表现。电荷转移在第一水化层上的定位也重现了非常强的OHO伸缩峰。此外，CO32-和CO3˙-水化能的巨大差异导致C-OH-O氢键长度的巨大差异，这表明CO3˙-的氧化是通过内球机制进行的。
