Kuznetsov Andrey M, Masliy Alexey N, Korshin Gregory V
Department of Inorganic Chemistry, Kazan National Research Technological University, K. Marx Street 68, Kazan, Russian Federation, 420015.
Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA, 98195-2700, USA.
J Mol Model. 2018 Jul 4;24(8):193. doi: 10.1007/s00894-018-3726-4.
Thermodynamic and structural aspects of the hydration of Pb(II) ions were explored based on DFT calculations combined with the supermolecular/continuum solvent model. Hydration of Pb(II) was considered as the formation of Pb(HO) aqua complexes (n=6-9) from the gas phase Pb(II) ion. Hexa- and hepta-aqua Pb(II) complexes were shown to exhibit the hemidirected symmetry, while those containing eight and nine water molecules are characterized by the holodirected symmetry. The calculations showed that because Pb(HO) complexes with six to nine water molecules have comparable thermodynamic stabilities, such complexes are likely to coexist in aqueous solutions. The deprotonation of Pb(HO) complexes was shown to result in the formation of the mono-hydroxo complex [Pb(HO)OH]. The pK value determined for this reaction (7.58 for Pb(HO)) was close to the experimental value of 7.61 used in recent models of aquatic equilibria. The density functional method ω-B97X(PCM-UAO) in combination with the atomic basis set 6-311++G(d,p) for O and H and the small-core electron effective pseudopotential (ECP) with the aug-cc-pvdz-PP basis set for Pb can be recommended for such calculations. Graphical abstract Structures of Pb(II) ions with varying numbers of water molecules in the inner hydration shell.
基于密度泛函理论（DFT）计算并结合超分子/连续介质溶剂模型，探究了Pb(II)离子水合作用的热力学和结构方面。将Pb(II)的水合作用视为气相Pb(II)离子形成Pb(HO)水合络合物（n = 6 - 9）的过程。已表明六水合和七水合Pb(II)络合物呈现半定向对称性，而含有八个和九个水分子的络合物具有全定向对称性。计算表明，由于含有六到九个水分子的Pb(HO)络合物具有相当的热力学稳定性，此类络合物可能在水溶液中共存。已表明Pb(HO)络合物的去质子化会导致形成单羟基络合物[Pb(HO)OH]。该反应的pK值（Pb(HO)为7.58）与近期水生平衡模型中使用的7.61实验值相近。对于此类计算，可推荐采用密度泛函方法ω - B97X(PCM - UA0)，结合用于O和H的6 - 311++G(d,p)原子基组以及用于Pb的具有aug - cc - pvdz - PP基组的小核电子有效赝势（ECP）。图形摘要内水化壳中具有不同水分子数的Pb(II)离子结构
