N, Ń-Bis[3-ethyl 2-azo(1-amino-8-hydroxy-nathalene-7-yl-3,5-disulphonic acid)- 4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylato-(N-4-chlorotriazino-6-yl)]-1, 4-phenylenediamine, Dye 1: blue, m.p. >300°C, yield 87%, λmax (H2O) 582.4 nm.

Figure 4: Structure of Dye 1.