title: Asequential Monte Carlo quantum mechanics study of the hydrogen-bond interaction and the solvatochromic shift of the n-pi* transition of acrolein in water.
abstract: The sequential Monte Carlo (MC) quantum mechanics (QM) methodology, using time-dependent density-functional theory (TD-DFT), is used to study the solvatochromic shift of the n-pi* transition of trans-acrolein in water. Using structures obtained from the isothermal-isobaric Metropolis MC simulation TD-DFT calculations, within the B3LYP functional, are performed for the absorption spectrum of acrolein in water. In the average acrolein makes one hydrogen bond with water and the hydrogen-bond shell is responsible for 30% of the total solvatochromic shift, considerably less than the shift obtained for the minimum-energy configurations. MC configurations are sampled after analysis of the statistical correlation and 100 configurations are extracted for subsequent QM calculations. All-electron TD-DFT B3LYP calculations of the absorption transition including acrolein and all explicit solvent molecules within the first hydration shell, 26 water molecules, give a solvatochromic shift of 0.18 +/- 0.11 eV. Using simple point charges to represent the solvent the shifts are calculated for the first, second, and third solvation shells. The results converge for the calculated shift of 0.20 +/- 0.10 eV in very good agreement with the experimentally inferred result of 0.20 +/- 0.05 eV. All average results presented are statistically converged.
authors.affiliation: Instituto de Física, Universidade de São Paulo, Caixa Postal 66318, 05315-970 São Paulo, São Paulo, Brazil.
authors.forename: Herbert C
authors.initials: HC
authors.lastname: Georg
authors.forename: Kaline
authors.initials: K
authors.lastname: Coutinho
authors.forename: Sylvio
authors.initials: S
authors.lastname: Canuto
mesh_terms: D000171:Acrolein / Q000737:chemistry*; D002627:Chemistry, Physical / Q000379:methods*; D004583:Electrons; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015233:Models, Statistical; D008968:Molecular Conformation; D009010:Monte Carlo Method; D011789:Quantum Theory; D012996:Solutions; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D012996:Solutions; D012997:Solvents; D014867:Water; D000171:Acrolein