title: p-Benzoquinone in aqueous solution: Stark shifts in spectra, asymmetry in solvent structure.
abstract: Results from a simulation of p-benzoquinone (PBQ) in water is presented. An explicit solvent representation is used together with a multiconfigurational ab initio quantum chemical method. The electronic n --> pi* transitions are studied in aqueous solution and the two such transitions are both blue-shifted but to different degree. Both non-equilibrium and many-body effects are found to have decisive influence on the solvation: despite stronger hydrogen bonding between solute and solvent in an excited state than in the ground state, there is a blue-shift, and the solvent structure around the non-polar PBQ is asymmetric, which is argued to come from special many-body effects. The unusual result of strengthened hydrogen bonds in the excited state that follows from an excitation of a non-bonding electron on a proton acceptor, is explained by the near-linear Stark shift that is present in the transition.
authors.affiliation: Department of Theoretical Chemistry, Chemical Centre, P.O.B 124, S-221 00 Lund, Sweden. anders.ohrn@teokem.lu.se
authors.forename: Anders
authors.initials: A
authors.lastname: Ohrn
authors.forename: Francesco
authors.initials: F
authors.lastname: Aquilante
mesh_terms: D016227:Benzoquinones / Q000737:chemistry*; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D012996:Solutions; D012997:Solvents / Q000737:chemistry*; D013057:Spectrum Analysis; D014867:Water / Q000737:chemistry*
chemical_list: D016227:Benzoquinones; D012996:Solutions; D012997:Solvents; D014867:Water; C004532:quinone