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

Abstract

Abstract The crystal structure of C.I. Pigment Yellow 1, α-(1-hydroxyethylidene) acetanilide-α-azo-(4′-methyl-2′-nitrobenzene), C17H16N4O4, has been determined by single crystal X-ray diffraction techniques. It crystallises in the monoclinic system with cell parameters a = 7.587 ± 0.042 Å, b = 20.362 ± 0.053 Å, c = 12.033 ± 0.046 Å, β = 120.68 ± 0.29°. The space group is P2 1/c and there are four molecules per unit cell. The structure was solved from that of C.I. Pigment Yellow 6 by isomorphous replacement, and least-squares refinement has been completed on three-dimensional data, 1696 reflections (CuKα radiation). The hydrogen atoms have been found and included but only those associated with the methyl groups have been refined. The final residual is 8.0%. The molecule exists as the hydrazone tautomer and intramolecular hydrogen bonds keep the molecule approximately planar. The molecules are packed in layers parallel to the (100) plane and in columns parallel to the a axis. Alternate molecules within the columns are in antiparallel position. The molecules are linked by van der Waals forces. Although the structure was solved from that C.I. Pigment Yellow 6, it is concluded that the two structures are not strictly isomorphous.