Hydroxybenzo[b]quinolizinium Ions: Water-Soluble and Solvatochromic Photoacids

Katy Schäfer; Heiko Ihmels; Cornelia Bohne; Karolina Papera Valente; Anton Granzhan

doi:10.1021/acs.joc.6b01991

Hydroxybenzo[b]quinolizinium Ions: Water-Soluble and Solvatochromic Photoacids

J Org Chem. 2016 Nov 18;81(22):10942-10954. doi: 10.1021/acs.joc.6b01991. Epub 2016 Nov 1.

Authors

Katy Schäfer¹, Heiko Ihmels¹, Cornelia Bohne², Karolina Papera Valente², Anton Granzhan³

Affiliations

¹ Department of Chemistry - Biology and Center of Micro and Nanochemistry and Engineering, University of Siegen , Adolf-Reichwein-Strasse 2, D-57068 Siegen, Germany.
² Department of Chemistry, University of Victoria , PO Box 1700 STN CSC, Victoria, BC Canada V8W 2Y2.
³ Institut Curie, PSL Research University and Université Paris Sud, Université Paris-Saclay, CNRS UMR9187, INSERM U1196 , F-91405 Orsay, France.

PMID: 27755869
DOI: 10.1021/acs.joc.6b01991

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 (pK_a* < 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.

Publication types

Research Support, Non-U.S. Gov't