The crystal structure of aceto-acetanilide azo-pigments II. C.I. Pigment Yellow 6, α-(1-hydroxyethylidene)acetanilide-α-azo-(4′-chloro-2′-nitrobenzene)

Abstract

Abstract The crystal structure of C.I. Pigment Yellow 6, α-(1-hydroxyethylidene)acetanilide-α-azo-(4′-chloro-2′-nitrobenzene) has been determined by single crystal X-ray diffraction techniques. It crystallises in the monoclinic system with cell parameters a = 7.462 ± 0.001 Å, b = 19.568 ± 0.002 Å, c = 11.175 ± 0.001 Å, β = 105.96 ± 0.01°. The space group is P21/n and there are four molecules per unit cell. The structure was solved using direct methods and least-squares refinement has been completed on three-dimensional data, 2504 reflections (CuKα radiation). The hydrogen atoms have been found and included, but only those associated with the methyl group have been refined. The final residual is 5.3%. The molecule exists as the hydrazone tautomer and intramolecular hydrogen bonds keep the molecule approximately planar, although the distortion in it is greater than in C.I. Pigment Yellow 3. The molecules are packed in columns parallel to the a axis with alternate molecules antiparallel and the molecules linked by van der Waals forces.