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The crystal structures of the azomethine nickel complexes Pigment Orange 68 (P.O.68, C 29 H 18 N 4 O 3 Ni), Pigment Red 257 (P.R.257, C 16 H 4 Cl 8 N 6 O 2 Ni), and Solvent Brown 53 (S.Br.53, C 18 H 10 N 4 O 2 Ni) were determined from powder diffraction data. The compounds are industrially used for the colouration of plastics and coatings. P.O.68 exists in two polymorphic forms, the commercial one is the α-phase. The crystal structures were solved from laboratory data using real-space methods and refined by the Rietveld method. For the Rietveld refinement of α-P.O.68, synchrotron data were employed. In all structures, the Ni 2+  ion is coordinated by two N atoms and two O atoms in a square-planar geometry. Both phases of P.O.68 crystallise in  P 2 1 / c ,  Z  = 4. In both structures, the molecules form dimers via an inversion centre, with Ni-to-Ni distances of 3.606 Å (α-phase) and 3.286 Å (β-phase). The dimers are stacked into columns. Neighbouring columns are connected by hydrogen bonds: one classical N–H⋅⋅⋅O bond, and one N–H⋅⋅⋅π bond to the naphthalene moiety of a molecule in the neighbouring stack. P.R.257 crystallises in  P 2 1 / c ,  Z  = 2, with molecules on inversion centres. The molecules show a typical van der Waals packing without close Ni-Ni contacts. S.Br.53 exhibits  Pbcn  symmetry with  Z  = 8. The molecules form columns with Ni-to-Ni distances of 3.508 Å.

Industrial azomethine nickel complex pigments. Four crystal structures from X-ray powder diffraction data