Testing the three step excited state proton transfer model by the effect of an excess proton

Rinat Gepshtein, Pavel Leiderman, Liat Genosar, Dan Huppert*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


In a previous work, we proposed an extended model for intermolecular excited-state proton transfer to the solvent. The model invoked an intermediate species, the contact ion-pair RO-⋯H3O+, where a proton is strongly hydrogen bonded to the conjugated photabase RO -*. In this study we tested the extended model by measuring the transient absorption and emission of 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) in an aqueous solution in the presence of a large concentration of mineral acids. In a neutral pH solution, the pump-probe signal consists of three time components, <1, 4, and 100 ps. The 4 ps time component, with a relative amplitude of about 0.3, was attributed to the formation of the contact ion-pair and the long 100 ps component to the dissociation of the ion-pair to a free proton and RO-*. In the presence of acid, the recombination of an excess proton competes with the geminate recombination. At a high acid concentration, the recombination process alters the time-dependent concentrations of the reactant, product and intermediate contact ion-pair. We observed that when the acid concentration increases, the amplitude of both the long and intermediate time components decreases. At about 3 M of acid, both components almost disappear. Model calculations of the acid effect on the transient HPTS signal indeed showed that the amplitude of the intermediate time component decreases as the excess proton concentration increases.

Original languageEnglish
Pages (from-to)9674-9684
Number of pages11
JournalJournal of Physical Chemistry A
Issue number42
StatePublished - 27 Oct 2005


Dive into the research topics of 'Testing the three step excited state proton transfer model by the effect of an excess proton'. Together they form a unique fingerprint.

Cite this