Structural investigations on four heterocyclic Disperse Red azo dyes having the same benzothiazole/azo/benzene skeleton

Four heterocyclic Disperse Red azo dyes having the same benzothiazole/azo/benzene skeleton, namely three classical C.I. Disperse Red 145, 152 and 153 (1–3) and another C.I. Disperse Red 153 substitute (4), have been structurally characterized and compared in this paper. X-ray single-crystal diffraction analyses reveal that they have similar planar molecular conformation between azo and aromatic units but dissimilar crystal packing fashions. In addition, different ratios of isomers have been found in the co-crystals of 3 and 4. To the best of our knowledge, this is the first structural report about the azo dyes having the benzothiazole/azo/benzene skeleton as well as co-crystal structures.

Graphical abstractFour heterocyclic Disperse Red azo dyes having the same benzothiazole/azo/benzene skeleton, namely three classical C.I. Disperse Red 145, 152 and 153 (1–3) and another C.I. Disperse Red 153 substitute (4), have been structurally characterized and compared. To our knowledge, this is the first structural report about the azo dyes having the benzothiazole/azo/benzene skeleton as well as co-crystal structures.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Four azo dyes 1–4 including C.I. Disperse Red 145, 152 and 153 are structurally characterized and compared. ► Four heterocyclic azo dyes have similar planar benzothiazole/azo/benzene skeleton. ► 3 and 4 have unique co-crystal structures having different ratios of isomers.