Several styrylquinolium salts were synthesized to investigate their absorption and thermal properties, which had five different p-aminobenzene units and three different counter ions (iodide, perchlorate, and hexafluorophosphorateanion), respectively.
Hydroxy, methoxy, and methyl group in the meta position to the amino group led to bathochromic shift, while N-ethyl-N-chloroethylamino unit instead of N,N-diethylamino unit resulted in hypsochromic shift.
A dye having a methoxy group in the meta position to the amino group had the highest molar extinction coefficient (e), while a dye carrying chloro group in N-alkyl chains had the lowest e.
The type of counter ions had no effect on spectral properties like the maximum absorption wavelength and e.
All styryl dyes had exothermic peaks at decomposition in DSC curves.
Among these styryl dyes, S2 series with perchlorate anions showed the strongest exothermic decomposition.
From TGA spectra, S3 series with hexafluorophosphorate anions had the best thermal stability and the sharpest threshold at thermal decomposition.