Single crystal X-ray structure analysis of some heterocyclic monoazo disperse dyes

Single crystal X-ray structures of monoazo disperse dyes comprising thiadiazolyl based diazo component and m-aminoacetanilide based coupling component were analysed and compared with a thiazolyl based monoazo disperse dye. It has been found that contrary to the earlier findings intramolecular hydrogen bonding between the β-nitrogen of the azo linkage and o-acetylamino substituent on the coupler is not the exclusive factor for the observed brightness of such dyes. An unequivocal evidence of the non-existence of such interaction has been presented.