Evaluation Procedure of Electrostatic Potential in 3D-RISM-SCF Method and Its Application to Hydrolyses of Cis- and Transplatin Complexes

Abstract

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.

Efficient implementation of the three-dimensional reference interaction site model method in the fragment molecular orbital method

“…40 These methods have been used to analyze the tautomerization of nucleobases, 41 hydrolysis of pyrophosphate, 42 and hydrolysis of transition metal complexes. 43 The results show good agreement with experimental observations and indicate the validity of the method. Furthermore, the 3D-RISM equation has been proven to be good at describing the solvation of biomolecules, so it is natural to also apply this method to electronic structure calculations for solvated biomolecules.…”

“…As mentioned in the Introduction, the 3D-RISM-SCF method has already been assessed for solvent effects on the electronic structures of solvated molecules. [41][42][43] For these FMO/3D-RISM calculations, r II = 16 Å and r III = 20 Å for exam37 were employed in this subsection.…”

“…(31) and (32) to avoid discontinuities at the border between regions II and III. 43 function is plotted against the radius in Figure 2. In this treatment, regions II and III should overlap, with r III < r II .…”

Hydration of Two Cisplatin Aqua-Derivatives Studied by Quantum Mechanics and Molecular Dynamics Simulations

“…Aono and Sakaki 59 have recently evaluated the reaction energies for the hydrolysis of cis-and trans-platin complexes undertaking a different approach based on the combined use of ab initio molecular orbital theory and liquid statistical theory (Reference Interaction Site model, RISM-SCF). 60,61 The general trend shown in Table 1 was already found by Aono and Sakaki.…”

Theoretical and Computational Study of a Complex System Consisting of Transition Metal Element(s): How to Understand and Predict Its Geometry, Bonding Nature, Molecular Property, and Reaction Behavior

“…This procedure is similar to that of the 3D-RISM-SCF method employed for transition metal complexes. 134,146 The geometry of the MM part is constructed by placing the QM molecule according to the symmetry of the crystal. The geometry optimization is carried out on the QM molecule, the QM-MM distance, and the orientation of the MM molecule (that is the lattice vectors), in a self-consistent manner under self-consistent charge distribution.…”