Table of Contents
ISRN Organic Chemistry
Volume 2011 (2011), Article ID 589012, 10 pages
http://dx.doi.org/10.5402/2011/589012
Research Article

Linear and Angular Distyrylpyrazines with Terminal Donor Groups: Synthesis, Solvatochromism, and Acidochromism of the Electronic Spectra

Institute for Organic Chemistry, Johannes Gutenberg-University Mainz, Duesbergweg 10–14, 55099 Mainz, Germany

Received 29 January 2011; Accepted 7 March 2011

Academic Editors: C. F. Chen and F. C. Pigge

Copyright © 2011 Volker Schmitt et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A series of linear and angular distyrylpyrazines and lateral donor groups has been prepared by aldol condensation between dimethylpyrazines and the appropriate aromatic aldehyde. The optical absorption and emission properties of these systems were studied in different solvents and media. The materials display a strong solvatochromism of the emission that is reflected by large red shifts of their fluorescence emission maxima on increasing the solvent polarity. This behaviour suggests a highly polar emitting state, which is characteristic of compounds that undergo an internal charge transfer upon excitation. Upon protonation, the UV-vis spectra are altered, and the fluorescence intensity of the neutral compound vanishes. These molecules can be used as colorimetric and luminescence polarity and pH sensors.