Shinji Aono

Publications (3)7.68 Total impact

• Article: Solution reaction space Hamiltonian based on an electrostatic potential representation of solvent dynamics.

  Shinji Aono, Takeshi Yamamoto, Shigeki Kato
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  ABSTRACT: Quantum chemical solvation models usually rely on the equilibrium solvation condition and is thus not immediately applicable to the study of nonequilibrium solvation dynamics, particularly those associated with chemical reactions. Here we address this problem by considering an effective Hamiltonian for solution-phase reactions based on an electrostatic potential (ESP) representation of solvent dynamics. In this approach a general ESP field of solvent is employed as collective solvent coordinate, and an effective Hamiltonian is constructed by treating both solute geometry and solvent ESP as dynamical variables. A harmonic bath is then attached onto the ESP variables in order to account for the stochastic nature of solvent dynamics. As an illustration we apply the above method to the proton transfer of a substituted phenol-amine complex in a polar solvent. The effective Hamiltonian is constructed by means of the reference interaction site model self-consistent field method (i.e., a type of quantum chemical solvation model), and a mixed quantum/classical simulation is performed in the space of solute geometry and solvent ESP. The results suggest that important dynamical features of proton transfer in solution can be captured by the present approach, including spontaneous fluctuations of solvent ESP that drives the proton from reactant to product potential wells.
  The Journal of chemical physics 04/2011; 134(14):144108. · 3.09 Impact Factor
• Article: Proton transfer in phenol-amine complexes: phenol electronic effects on free energy profile in solution.

  Shinji Aono, Shigeki Kato
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  ABSTRACT: Free energy profiles for the proton transfer reactions in hydrogen-bonded complex of phenol with trimethylamine in methyl chloride solvent are studied with the reference interaction site model self-consistent field method. The reactions in both the electronic ground and excited states are considered. The second-order Møller-Plesset perturbation (MP) theory or the second-order multireference MP theory is used to evaluate the effect of the dynamical electron correlation on the free energy profiles. The free energy surface in the ground state shows a discrepancy with the experimental results for the related hydrogen-bonded complexes. To resolve this discrepancy, the effects of chloro-substitutions in phenol are examined, and its importance in stabilizing the ionic form is discussed. The temperature effect is also studied. In contrast to the ground state, the ππ* excited state of phenol-trimethylamine complex exhibits the proton transfer reaction with a low barrier. The reaction is almost thermoneutral. This is attributed to the reduction of proton affinity of phenol by the ππ* electronic excitation. We further examine the possibility of the electron-proton-coupled transfer in the ππ* state through the surface crossing with the charge transfer type πσ* state.
  Journal of Computational Chemistry 12/2010; 31(16):2924-31. · 4.58 Impact Factor
• Article: Theoretical Study of Electrostatic Solvent Effects within Free Energy Expression and Application to Solvated Reaction

  Shinji Aono
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  ABSTRACT: Kyoto University (京都大学) 0048 新制・課程博士 博士(理学) 甲第15633号 理博第3579号 新制/理/1522 28170 2010-09-24 京都大学大学院理学研究科化学専攻 (主査)准教授 林 重彦, 教授 谷村 吉隆, 教授 松本 吉泰 学位規則第4条第1項該当