A sequential Monte Carlo quantum mechanics study of the hydrogen-bond interaction and the solvatochromic shift of the n-pi transition of acrolein in water

摘要

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-aciolein 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.