Reference interaction site model self-consistent field study for solvation effect on carbonyl compounds in aqueous solution

TLDR

Previous studies have explored solvation effects on electronic structure, and a new computational procedure combining RISM and Hartree–Fock was developed. The study applies this RISM–Hartree–Fock method to several carbonyl compounds in aqueous solution. The method simultaneously computes solvent distribution and solute electronic wave functions using RISM coupled with Hartree–Fock, employs the SPC water model, and applies this framework to calculate vertical electronic transitions and excited‑state free energies for formaldehyde to estimate fluorescence contributions. The intramolecular energy contributes significantly to the bathochromic shift of fluorescence in aqueous solution, and calculations on acetaldehyde, acetone, and acrolein highlight the structural influence of functional groups.

Abstract

In the previous study, Chem. Phys. Lett. 214, 391 (1993), we developed a new computational procedure for the solvation effect on the electronic structure of solute based upon the reference interaction site model (RISM) integral equation and the Hartree–Fock equation. The method enables us to calculate the solvent distribution and solute electronic wave functions simultaneously, which is free from such empirical parametrizations as appeared in the usual models based on the dielectric continuum picture. In the present article, we have applied the method to several carbonyl compounds in aqueous solution. The SPC model was used to describe the liquid water. The vertical n→π*, π→π*, and σ→π* transitions of formaldehyde are examined by the RISM-self-consistent field formalism coupled with the restricted Hartree–Fock approximation, and then the free energy calculation was performed for the excited state in order to estimate the contributions for the optical fluorescence spectra. The intramolecular energy turned out to give significant contribution to the bathochromic shift of fluorescence relative to the absorption in the liquid phase. Furthermore the importance of the structural effect of the functional group was discussed by the calculations of three more carbonyl compounds, acetaldehyde, acetone, and acrolein.