Reactive Dyes Bearing Bis(Monochlorotriazine) Group: Synthesis, Photophysical Properties and Realization of Salt-Free Dyeing

A series of novel reactive dyes D1–D3 based on vinamidinium salt were designed and synthesized. Bis(monochlorotriazine) was introduced as the reactive group and sodium sulfonate was the water-soluble group. Their photophysical properties were studied systematacially. The strong and sharp ground-state absorption peak in the 250–320 nm range in the UV-vis absorption spectrum of the aqueous solution could be attributed to the ¹π–π* transition by the parent structure of the dyes, and the relatively broad absorption peak in the range of 300–650 nm could be attributed to the ¹π–π* mixed intramolecular charge transfer. By applying this series of reactive dyes to the dyeing of four fabrics (silk, cotton, polyester/cotton blends, and polyester), the dyeing depths were in the range of 5.2–28.6 under salt-free conditions. The results show that D3 with higher planarity can increase the dyeing depth. At length, fastening tests on dyed cotton fabrics and silk showed that this series of reactive dyes had a color fastness between grades 3 and 5 for abrasion and soap-washing. In summary, these reactive dyes could be potential dyes for salt-free dyeing applications.