title: Ultraviolet Absorption Spectrum of Malonaldehyde in Water Is Dominated by Solvent-Stabilized Conformations.
abstract: Free energy calculations for eight enol isomers of malonaldehyde (MA) and simulation of the ultraviolet (UV) absorption spectrum in both the gas phase and water (pH = 3, where the molecule exists in neutral undeprotonated form) show that in water the two s-trans nonchelated enol conformers of MA become thermodynamically more stable than the internally hydrogen-bonded ("chelated enol") conformer (CE). The pure CE conformer in water has a slightly red-shifted UV spectrum with respect to that in the gas phase, but the blue-shifted spectrum observed in water at pH 3 is dominated by solvent-stabilized conformations that have negligible populations in the gas phase. Density functional calculations with the solvation model based on density (SMD) and an ensemble-averaged vertical excitation model explain the experimental observations in detail.
authors.affiliation: Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Xuefei
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States.
authors.forename: Donald G
authors.initials: DG
authors.lastname: Truhlar