Delocalized cationic azo dyes containing a thiazole moiety

Several new delocalized cationic azo dyes incorporating a bathochromic thiazole moiety have been prepared in moderate to good yields. The synthesis involved the Knoevenagel condensation of an intermediate azo compound, bearing a terminal formyl group, with methylenic bases generated in situ from benzoazolium and quinolinium salts. All dyes display strong absorption around 700 nm and have shown negative solvatochromic behaviour.

Graphical abstractDownload full-size image Several new delocalized cationic azo dyes incorporating a bathochromic thiazole moiety have been prepared in moderate to good yields. All dyes display very strong absorption around 700 nm and have shown negative solvatochromic behaviour.