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Issue 9, 2012
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Influence of pH on photophysical properties of (E)-1-(4-chlorobenzyl)-4-(4-hydroxystyryl)pyridinium chloride

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The protonation/deprotonation equilibrium was investigated for N-p-chlorobenzyl-substituted (E)-4′-hydroxy stilbazolium halide, namely (E)-1-(4-chlorobenzyl)-4-(4-hydroxystyryl)pyridinium chloride (EPC). Absorption, emission and synchronous scanning spectra were used to explain the observed phenomena. The excited state lifetimes of the protonated and deprotonated forms of EPC were measured and discussed. Absorption spectra were used to determine its pKa value in the ground state. We conclude that the protonation/deprotonation equilibrium is not attained in the first excited state of EPC, for kinetic reasons. The quinoid and benzenoid structures of EPC in the ground and excited state are discussed in acidic and basic range of pH. Aqueous solutions of EPC were yellow at pH < 7 and red at pH > 7, and addition of alcohols (methanol or 2-propanol) enhanced this change. Therefore, quaternary stilbazolium salts were investigated for application as acid–base indicators.

Graphical abstract: Influence of pH on photophysical properties of (E)-1-(4-chlorobenzyl)-4-(4-hydroxystyryl)pyridinium chloride

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Supplementary files

Article information

30 Jan 2012
07 Jun 2012
First published
13 Jun 2012

Photochem. Photobiol. Sci., 2012,11, 1454-1464
Article type

Influence of pH on photophysical properties of (E)-1-(4-chlorobenzyl)-4-(4-hydroxystyryl)pyridinium chloride

D. Prukała, W. Prukała, M. Gierszewski, J. Karolczak, I. Khmelinskii and M. Sikorski, Photochem. Photobiol. Sci., 2012, 11, 1454
DOI: 10.1039/C2PP25063B

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