title: Femtosecond pump-probe measurements of solvation by hydrogen-bonding interactions.
abstract: An additional ultrafast blue shift in the transient absorption spectra of hydrogen-bonding complexes of a strong photoacid, 8-hydroxypyrene 1,3,6-trisdimethylsulfonamide (HPTA), over the solvation response of the uncomplexed HPTA and also over that of the methoxy derivative of the photoacid (MPTA) in the presence of the hydrogen-bonding base was observed on optical excitation of the photoacid. The additional 55 +/- 10 fs solvation response was found to be about 35 % and 19% of the total C(t) of HPTA in dichloromethane (DCM) when it was hydrogen-bonded to dimethylsulfoxide (DMSO) and dioxane, respectively, and about 29% of the total C(t) of HPTA in dichloroethane (DCE) when it was hydrogen-bonded to DMSO. We have assigned this additional dynamic spectral shift to a transient change in the hydrogen bond (O-H...O) that links HPTA to the complexing base, after the electronic excitation of the photoacid.
authors.affiliation: Chemistry Department, Ben-Gurion University of the Negev P.O.B. 653, Beer-Sheva 84105, (Israel). epines@bgumail.bgu.ac.il
authors.forename: Ehud
authors.initials: E
authors.lastname: Pines
authors.forename: Dina
authors.initials: D
authors.lastname: Pines
authors.forename: Ying-Zhong
authors.initials: YZ
authors.lastname: Ma
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming