We address the aqueous microsolvation of the CH₃HgCl and CH₃HgOH molecules using a stepwise hydration scheme including up to 33 water molecules and compare our results with the previously studied HgCl₂, HgClOH, and Hg(OH)₂ complexes. Optimized geometries and Gibbs free energies were obtained at the B3PW91/aug-RECP(Hg)-6-31G(d,p) level. At least 33 water molecules were required to build the first solvation shell around both methylmercury compounds. Optimized geometries were found having favorable interactions of water molecules with Hg, Cl, and the OH moiety. Born-Oppenheimer molecular dynamics simulations were performed on the largest CH₃HgX(X = Cl, OH)–(H₂O)₃₃ clusters at the same level of theory. Born-Oppenheimer molecular dynamics simulations at T = 300 K (ca. 0.62 kcal/mol) revealed the presence of configurations with hydrogen-bonded networks that include the OH moiety in CH₃HgOH and exclude both the Hg and Cl in CH₃HgCl, favoring a clathrate-type structure around the methyl moiety. The comparison to the microsolvated HgClOH, Hg(OH)₂, and HgCl₂ molecules showed that, in all cases, the water molecules easily move away from Cl, thus supporting the idea that HgCl₂ behaves as a non-polar solute. The theoretical (L_III edge) X-ray absorption near edge structure spectra are obtained and found in good agreement with experimental data, especially for the CH₃HgCl species.

中文翻译：

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与HgCl2，HgClOH和Hg（OH）2相比，CH3HgOH和CH3HgCl的水合：DFT微溶剂簇方法

我们使用逐步水化方案（包括多达33个水分子）解决了CH ₃ HgCl和CH ₃ HgOH分子的水微溶剂化问题，并将我们的结果与先前研究的HgCl ₂，HgClOH和Hg（OH）₂配合物进行了比较。在B3PW91 / aug-RECP（Hg）-6-31G（d，p）水平下获得了最佳的几何形状和吉布斯自由能。至少需要33个水分子才能围绕两种甲基汞化合物构建第一个溶剂化壳。发现优化的几何结构具有水分子与Hg，Cl和OH部分的良好相互作用。对最大的CH ₃ HgX（X = Cl，OH）–（H ₂ O）₃₃进行Born-Oppenheimer分子动力学模拟在相同的理论水平上集群。在T = 300°K出生-奥本海默分子动力学模拟（约0.62千卡/摩尔）揭示了与氢键合网络，包括在CH OH部分的配置的存在₃ HgOH和在CH排除两个汞和Cl ₃的HgCl，有利于围绕甲基部分的笼形结构。与微溶剂化的HgClOH，Hg（OH）₂和HgCl ₂分子的比较表明，在所有情况下，水分子都容易从Cl移开，从而支持HgCl ₂表现为非极性溶质的观点。理论（L _III获得了边缘结构附近的X射线吸收光谱，发现与实验数据非常吻合，特别是对于CH ₃ HgCl物种。