Ionic perylene-3,4-dicarboximide as chromonic mesogens and the use of a fluorescence technique in determining phase-transition temperatures

Abstract

We report a study of the chromonic liquid-crystalline properties of 2-(N,N-diethyl-N-methylammonium)ethylperylene-3,4-dicarboximide formate (1) in aqueous solution by polarised optical microscopy (POM), ²H nuclear magnetic resonance (NMR) spectroscopy and fluorescence spectroscopy. Compound 1 shows chromonic liquid-crystalline properties at concentrations higher than 4 wt% at room temperature. We showed that fluorescence spectroscopy could be used to determine the concentration-dependent, phase-transition temperatures of this chromonic liquid crystal. The values determined by fluorescence spectroscopy are consistent with the values determined by ²H NMR spectroscopy and POM.

Keywords:

• chromonic liquid crystals
• supramolecular chemistry
• aggregation
• fluorescence

Acknowledgements

This material is based on work supported by the National Science Foundation under Grant No. DMR 0405532 and DMR 0804897. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. We thank Thomas Frontino, one of our undergraduate students, for his help in performing some of the preliminary studies of the liquid-crystalline properties of 1.