(Dialkylamino)thiazole dimers act as very strong electron-donating coupling
components in azo dyes, the first and second UV-VIS absorption bands of wh
ich were observed at lambda = 568-737 (epsilon = 24000-88000) and 404-475 (
epsilon = 9200-52000) nm in dichloromethane, respectively. The azo compound
s derived from the (dialkylamino)thiazole dimers having very strong electro
n-withdrawing moieties such as 4-(perfluoroalkylsulfonyl)phenyls, 2,4-dinit
rophenyl, and thiazol-2-yls exhibited a negative solvatochromism. This is t
he first example of a negative solvatochromism in neutral azo dyes.