SPECTROSCOPIC STUDIES OF A POLARITY-SENSITIVE PYRENYL DYE

Aryl dyes may be prepared using simple synthetic steps, e.g., by condensation of an arylcarboxaldehyde with a quaternary salt of a heterocycle having a methyl group in the 2-or 4-position. This paper focuses on the spectral properties and analytical applications of one of the aryl derivatives prepared in our laboratory. 1-Pyrenecarboxaldehyde was condensed with 3-ethyl-2-methylbenzothiazolium to form an aryl dye. The absorption and fluorescence properties of this dye were found to be strongly dependent on solvent hydrophobicity. The chromophore has an absorption maximum at 562 nm in methanol and at 619 nm in aqueous solutions. The relative ratios of the vibronic bands of the fluorescence from the pyrene moiety also change as the polarity of the environment changes. The observed excimer band is similar to that of the underivatized pyrene molecule. Fluorescence energy transfer from the aryl to the chromophore portion of the molecule was also observed. The analytical utility of these phenomena has been evaluated. © 1992.