I  U  P  A  C




News & Notices

Organizations & People

Standing Committees




. . CI
. . PAC
. . Macro. Symp.

. . Books
. . Solubility Data



Links of Interest

Search the Site

Home Page


Pure Appl. Chem. 76(10), 1903-1919, 2004

Pure and Applied Chemistry

Vol. 76, Issue 10

Pyridinium N-phenolate betaine dyes as empirical indicators of solvent polarity: Some new findings

C. Reichardt

Department of Chemistry, Philipps University, Hans-Meerwein-Strasse, D-35032 Marburg, Germany

Abstract: Solutions of the zwitterionic betaine dye 4-(2,4,6-triphenylpyridinium-1-yl)-2,6-di- phenylphenolate are solvatochromic, thermochromic, piezochromic, and halochromic. That means the position of its longest-wavelength intramolecular charge-transfer absorption band depends on solvent polarity, solution temperature, external pressure, and the nature and concentration of added salts. The extraordinarily large negative solvatochromism of this standard betaine dye has been used to establish UV/vis spectroscopically an empirical scale of solvent polarity, called ET(30), respectively ETN scale, meanwhile known for many organic solvents and solvent mixtures. In this review, the solvatochromic properties of some new hydrophilic and lipophilic betaine dyes with better solubility in water (respectively, nonpolar solvents), as well as some recent applications of these betaine dyes in various fields of interest [e.g., microheterogeneous (micellar) and polymer solutions, chemical sensors, as well as surface polarity of silicas, aluminas, and cellulose derivatives] are described.

*Plenary lecture presented at the 28th International Conference on Solution Chemistry, Debrecen, Hungary, 23-28 August 2003. Other presentations are published in this issue, pp. 1809-1919.

Page last modified 21 October 2004.
Copyright © 2004 International Union of Pure and Applied Chemistry.
Questions or comments about IUPAC, please contact, the Secretariat.
Questions regarding the website, please contact web manager.