title: Hydroxybenzo[b]quinolizinium Ions: Water-Soluble and Solvatochromic Photoacids.
abstract: It is shown by photometric and fluorimetric analysis, along with supporting theoretical calculations, that hydroxy-substituted benzo[b]quinolizinium derivatives display the characteristic features of organic photoacids. Specifically, the experimental and theoretical results confirm the strong acidity of these compounds in the excited state (pKa* < 0). The combination of the prototropic properties of 8- and 9-hydroxybenzo[b]quinolizinium with the particular solvent-solute interactions of the excited acid and its conjugate base leads to a pronounced fluorosolvatochromism, hence the emission maxima shift from 468 nm (8-hydroxybenzo[b]quinolizinium) or 460 nm (9-hydroxybenzo[b]quinolizinium) in CH3CN to 507 and 553 nm in DMF, respectively. This novel type of photoacid represents several features that may be used for applications as water-soluble fluorescent probes or as a source for the photoinduced supply of acidity.
authors.affiliation: Department of Chemistry - Biology and Center of Micro and Nanochemistry and Engineering, University of Siegen , Adolf-Reichwein-Strasse 2, D-57068 Siegen, Germany.
authors.forename: Katy
authors.initials: K
authors.lastname: Schäfer
authors.affiliation: Department of Chemistry - Biology and Center of Micro and Nanochemistry and Engineering, University of Siegen , Adolf-Reichwein-Strasse 2, D-57068 Siegen, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Ihmels
authors.affiliation: Department of Chemistry, University of Victoria , PO Box 1700 STN CSC, Victoria, BC Canada V8W 2Y2.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Bohne
authors.affiliation: Department of Chemistry, University of Victoria , PO Box 1700 STN CSC, Victoria, BC Canada V8W 2Y2.
authors.forename: Karolina Papera
authors.initials: KP
authors.lastname: Valente
authors.affiliation: Institut Curie, PSL Research University and Université Paris Sud, Université Paris-Saclay, CNRS UMR9187, INSERM U1196 , F-91405 Orsay, France.
authors.forename: Anton
authors.initials: A
authors.lastname: Granzhan