Pyridinium 5-aminothiazoles: specific photophysical properties and vapochromism in halogenated solvents

Treatment of pyridyl-5-aminothiazoles (1–4) with alkyl triflates or benzyl iodide afforded the corresponding pyridinium 5-aminothiazoles (5–10), which exhibited bathochromically shifted absorption and fluorescence spectra relative to those of 1–4. Moreover, the vapochromic properties of 5 specific to halogenated solvents were examined by powder X-ray diffraction analysis. Pmma films containing 5 can thus be used to detect halogenated solvents, especially CH2Cl2.