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.

Despite strong electrostatic repulsion, likecharged ions in aqueous solution can effectively attract each other via ion−water interactions. In this paper we investigate such an effective interaction of like-charged ions in water by using the 3D-RISM-SCF method (i.e., electronic structure theory combined with three-dimensional integral equation theory for molecular solvents). Free energy profiles are calculated at the CCSD(T) level for a series of molecular ions including guanidinium (Gdm + ), alkyl-substituted ammonium, and aromatic amine cations. Polarizable continuum model (PCM) and mean-field QM/MM free energy calculations are also performed for comparison. The results show that the stability of like-charged ion pairs in aqueous solution is determined by a very subtle balance between interionic interactions (including dispersion and π-stacking interactions) and ionic solvation/hydrophobic effects and that the Gdm + ion has a rather favorable character for like-charge association among all the cations studied. Furthermore, we investigate the like-charge pairing in Arg-Ala-Arg and Lys-Ala-Lys tripeptides in water and show that the Arg-Arg pair has a contact free-energy minimum of about −6 kcal/mol. This result indicates that arginine pairing observed on protein surfaces and interfaces is stabilized considerably by solvation effects.

The first examples of porousm olecular crystals that are assembled through Au···Au interactions of gold complex 1 are here reporteda long with their exchange properties with respect to their guestc omponents.S inglecrystal X-ray diffraction (XRD) analyses indicatet hat the crystal structure of 1/CH 2 Cl 2 ·pentane is based on cyclic hexamers of 1,w hich are formedt hrough six Au···Au interactions. The packingo ft hese cyclic hexamers affords ap orousa rchitecture, in which the one-dimensionalc hannel segmentc ontains CH 2 Cl 2 and pentane as guests. These guestsc an be ex-changed through operationally simple methods under retention of the host framework of 1,w hich furnished 1/guest complexes with 26 differentg uests.As ingle-crystal XRD analysiso f1/eicosane, which contains the long linear alkane eicosane (n-C 20 H 42 ), successfully provided its accurately modeled structurew ithin the porous material. These host-guest complexes show chromic luminescence with both blue-and redshifted emissions.M oreover,t his porouso rganometallic materialcan exhibit luminescentmechanochromism through release of guests.[a] Dr.Figure 10. Emission spectra of 1/CH 2 Cl 2 ·pentane(blue line)and 1 ground (green line). Inset shows aphotographo f1 ground recorded under UV light.Figure 9. a) Optimized triplet structure of 1/CH 2 Cl 2 ·pentane.b )Upper and c) lowerS OMO of the optimized triplet structure of 1/CH 2 Cl 2 ·pentane. Ad etailed description of the modeling and calculation conditionsisg iven in the Supporting Information.

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One of the difficulties in application of the usual reference interaction site model self-consistent field (RISM-SCF) method to a highly polarized and bulky system arises from the approximate evaluation of electrostatic potential (ESP) with pure point charges. To improve this ESP evaluation, the ESP near a solute is directly calculated with a solute electronic wavefunction, that distant from a solute is approximately calculated with solute point charges, and they are connected with a switching function. To evaluate the fine solvation structure near the solute by incorporating the long-range solute-solvent Coulombic interaction with low computational cost, we introduced the dual solvent box protocol; one small box with the fine spacing is employed for the first and the second solvation shells and the other large box with the normal spacing is employed for long-range solute-solvent interaction. The levoglucosan formation from phenyl α- and β-d-glucosides under basic conditions is successfully inspected by this 3D-RISM-SCF method at the MP2 and SCS-MP2 levels, though the 1D-RISM-SCF could not be applied to this reaction due to the presence of highly polarized and bulky species. This 3D-RISM-SCF calculation reproduces the experimentally reported higher reactivity of the β-anomer. The 3D-RISM-SCF-calculated activation free energy for the β-anomer is closer to the experimental value than the PCM-calculated one. Interestingly, the solvation effect increases the difference in reactivity between these two anomers. The reason is successfully elucidated with 3D-RISM-SCF-calculated microscopic solvation structure and decomposition analysis of solute-solvent interaction.