1999 Fiscal Year Final Research Report Summary
Reaction dynamics of excited state molecules in solution
| Project/Area Number |
09440200
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
KATO Shigeki Professor, Department of Chemistry Graduate School of Science, Kyoto University, 大学院・理学研究科, 教授 (20113425)
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| Project Period (FY) |
1997 – 1999
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| Keywords | dynamics / excited state / solution / ab initio calculation / molecular dynamics / electron polarization / integral equation / dielectric relaxation |
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| Research Abstract |
Electron polarization of solvent is known to play an important role in the dynamics of molecular processes in solution. We proposed the charge response kernel (CRK) which was defined as the second derivatives of molecular electronic energy with respect to the electrostatic potentials acting on the molecular interaction sites in order to represent the charge polarization in solute and solvent molecules in solution. The CRK matrix can be easily calculated by ab initio molecular orbital calculations. We examined the effect of electronic polarization on the diffusion of radical in solution. It has been experimentally observed that the diffusion constant of radical species generated by photo-initiated hydrogen abstraction from a solvent molecule is larger than that of the parent molecule. In order to elucidate those experiments. we carried out molecular dynamics calculations of pyrazine and pyrazinyl radical in methanol. We also studied the effect of solvent fluctuation on solute electronic
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excitation energies using the RISM-SCF method. The results were presented for (1) the solvent spacial fluctuation effect on the absorption spectral profile of formaldehyde in aqueous solution, (2) the solvent electronic polarization effect on the vertical excitation energies of acetone and pyridine, and (3) the time-dependent RISM-SCF approach to the dielectric relaxation of solvents initiated by the electronic excitation of benzonitrile. In order to estimate the fluctuation of electrostatic potential acting on the solute interaction sites coming from the solvent spacial fluctuation, we assumed a Gaussian distribution with the covariance matrix derived by RISM-SCF calculations and calculated the distribution of solute excitation energies with the set of electrostatic potentials generated according to the Gaussian distribution function. The contribution from solvent vibrations were also examined. The CRK method was utilized to develop the charge polarizable RISM-SCF method, which incorporate the solvent electronic polarization around the solute molecule. We took nonpolar polarizable molecules such as acetonitrile, chloroform, carbon tetrachloride and carbon disulfide as solvents in examining the solvent electronic poladzation effects on the solute vertical excitation energies. It was shown that the contribution of solvent electronic polarization to the solvation shifts was well related to the diffraction index of solvents. A time-dependent RISM-SCF method was further proposed by combining with the linear response theory for solvent relaxation dynamics. Difference in time-dependent Stokes shifts for water, methanol and acetonitrile solutions was discussed. Less
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Research Products
(20 results)
