The crystal structure of CI Pigment Yellow 97, a superior performance Hansa yellow pigment

CI Pigment Yellow 97 is one of the most important industrial Hansa yellow monoazo pigments because of its superior technical performance in application. Crystals of this pigment are triclinic. The molecule adopts the ketohydrazone form in its crystal structure and there is strong intramolecular hydrogen bonding. The molecule deviates significantly from planarity. The phenyl ring of the phenylsulfonamide group is positioned like an open lid, making an angle of 52.21(11)° with the arylhydrazone ring. There is also a degree of intermolecular hydrogen bonding between sulfonamide groups in adjacent molecules. The relationship between features seen in the crystal structure and the technical performance of this pigment are discussed, particularly with regard to the role of the phenylsulfonamide group.