Excited-state proton transfer in N-methyl-6-hydroxyquinolinium salts: Solvent and temperature effects

Elizabeth Ann Gould, Alexander V. Popov, Laren M. Tolbert, Itay Presiado, Yuval Erez, Dan Huppert, Kyril M. Solntsev*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

The excited-state proton transfer (ESPT) reaction of the "super"photoacid N-methyl-6-hydroxyquinolinium (MHQ) was studied using both fluorescence upconversion and time-correlated single photon counting (TCSPC) techniques. The ultrafast ESPT kinetics were investigated in various alcohols and water and determined to be solvent-controlled. The ESPT temperature dependence of MHQ was also studied in various alcohols and compared to that observed for another "super"photoacid, 5,8-dicyano-2-naphthol (DCN2). A full set of kinetic and thermodynamic parameters describing the ESPT was obtained. The protolytic photodissociation rate constant for MHQ was higher than that for DCN2, while the ESPT activation energies of MHQ were smaller. These findings are attributed to the approximately 3 orders of magnitude differences in excited-state acidities of MHQ and DCN2.

Original languageEnglish
Pages (from-to)8964-8973
Number of pages10
JournalPhysical Chemistry Chemical Physics
Volume14
Issue number25
DOIs
StatePublished - 7 Jul 2012

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