Near-infrared absorbing delocalized cationic azo dyes

摘要

Novel, delocalized, cationic azo dyes derived from benzothiazole, benzoselenazole, indole and quinoline, displaying strong absorption around 700-800 nm, have been prepared in moderate to good yields. The synthesis involved the Knoevenagel condensation of an intermediate azo compound, possessing a 4-chloro-5-formylthiazole moiety, with methylenic bases generated in situ from benzoazolium and qui-nolinium salts.