Fukui Institute for Fundamental Chemistry, Kyoto University, Sakyao-ku, Kyoto, Japan.
J Phys Chem B. 2012 Nov 1;116(43):13045-62. doi: 10.1021/jp307879j. Epub 2012 Oct 19.
In the three-dimensional reference interaction site model self-consistent field (3D-RISM-SCF) method, a switching function was introduced to evaluate the electrostatic potential (ESP) around the solute to smoothly connect the ESP directly calculated with the solute electronic wave function and that approximately calculated with solute point charges. Hydrolyses of cis- and transplatins, cis- and trans-PtCl(2)(NH(3))(2), were investigated with this method. Solute geometries were optimized at the DFT level with the M06-2X functional, and free energy changes were calculated at the CCSD(T) level. In the first hydrolysis, the calculated activation free energy is 20.8 kcal/mol for cisplatin and 20.3 kcal/mol for transplatin, which agrees with the experimental and recently reported theoretical results. A Cl anion, which is formed by the first hydrolysis, somehow favorably exists in the first solvation shell as a counteranion. The second hydrolysis occurs with a similar activation free energy (20.9 kcal/mol) for cisplatin but a somewhat larger energy (23.2 kcal/mol) for transplatin to afford cis- and trans-diaqua complexes. The Cl counteranion in the first solvation shell little influences the activation free energy but somewhat decreases the endothermicity in both cis- and transplatins. The present 3D-RISM-SCF method clearly displays the microscopic solvation structure and its changes in the hydrolysis, which are discussed in detail.
在三维参考相互作用位点模型自洽场（3D-RISM-SCF）方法中，引入了一个开关函数来评估溶质周围的静电势（ESP），以平滑连接直接用溶质电子波函数计算的 ESP 和用溶质点电荷近似计算的 ESP。采用该方法研究了顺铂和反铂、顺式-和反式-PtCl2(NH3)2的水解反应。在 M06-2X 泛函水平上优化了溶质的几何形状，并在 CCSD(T)水平上计算了自由能变化。在第一次水解中，计算得到的顺铂和反铂的活化自由能分别为 20.8 kcal/mol 和 20.3 kcal/mol，与实验和最近报道的理论结果一致。由第一次水解形成的 Cl-阴离子作为抗衡离子以某种方式有利地存在于第一个溶剂化壳中。对于顺铂，第二次水解以相似的活化自由能（20.9 kcal/mol）发生，但对于反铂，能量稍大（23.2 kcal/mol），以生成顺式和反式二水合络合物。第一个溶剂化壳中的 Cl-抗衡阴离子对活化自由能的影响不大，但对顺铂和反铂的吸热性都有一定程度的降低。本 3D-RISM-SCF 方法清楚地显示了水解过程中的微观溶剂化结构及其变化，并进行了详细讨论。
