Structures of six industrial benzimidazolone pigments from laboratory powder diffraction data

Monoazo (Monohydrazone) pigments based on benzimidazolones

A series of azo pigments containing the benzimidazolone ring were introduced in the mid to late twentieth century as high-performance organic pigments in the yellow, orange, red, and brown shade areas. The structures of the commercial benzimidazolone azo pigments are derived from either the monoazoacetoacetanilide or monoazonaphtharylamide classical azo pigments systems and exist in the ketohydrazone tautomeric forms. The high-performance properties of the pigments have been attributed to a network of intermolecular hydrogen bonds involving the benzimidazolone group, and efficient molecular packing, as demonstrated by X-ray crystal structure determinations. The manufacturing processes leading to the pigments involve traditional diazotization and azo coupling reaction procedures, although they require special conditioning aftertreatments to optimize their performance. Although benzimidazolone azo pigments were initially developed for the coloration of plastics, they have probably had a greater impact on the paint industry. The application properties of the benzimidazolone azo pigments are discussed for individual products.

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

The crystal structures of the azomethine nickel complexes Pigment Orange 68 (P.O.68, C29H18N4O3Ni), Pigment Red 257 (P.R.257, C16H4Cl8N6O2Ni), and Solvent Brown 53 (S.Br.53, C18H10N4O2Ni) 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 Ni2+ ion is coordinated by two N atoms and two O atoms in a square-planar geometry. Both phases of P.O.68 crystallise in P21/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 P21/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.

Metal-Free Synthesis of N-(Carboselenoate) Benzimidazolones by Cascade Cyclization of ortho-Diisocyanoarenes and Selenosulfonates

A facile synthesis of N-(carboselenoate) benzimidazolones through metal-free reactions of ortho-diisocyanoarenes with selenosulfonates is reported here. The desired products are obtained in moderate to good yields with good functional group compatibility. The ortho-diisocyanoarenes are applied to the construction of 2-benzimidazolone derivatives for the first time.

Direct-space solution in theEXPOpackage: the combination of the HBB–BC algorithm with GRASP

The hybrid big bang–big crunch algorithm is a combination of a global optimization algorithm inspired by one of the theories of the evolution of the universe, named the big bang and big crunch theory, and the simulated annealing method. The procedure was implemented in the latest version of the programEXPOand applied to crystal-structure solution from powder diffraction data. Several aspects of the hybrid big bang–big crunch algorithm can be further optimized with the aim of obtaining good quality solutions in a shorter computation time. In the present study, the hybrid big bang–big crunch procedure has been combined with the greedy randomized adaptive search procedure (GRASP) and some steps of the algorithm have been improved. The new approach, implemented in theEXPOpackage, has been successfully tested on numerous known crystal structures.

Improved performance of crystal structure solution from powder diffraction data through parameter tuning of a simulated annealing algorithm

Significant gains in the performance of the simulated annealing algorithm in theDASHsoftware package have been realized by using theiraceautomatic configuration tool to optimize the values of three key simulated annealing parameters. Specifically, the success rate in finding the global minimum in intensity χ2space is improved by up to an order of magnitude. The general applicability of these revised simulated annealing parameters is demonstrated using the crystal structure determinations of over 100 powder diffraction datasets.

Improved crystal structure solution from powder diffraction data by the use of conformational information

The effect of introducing conformational information to theDASHimplementation of crystal structure determination from powder diffraction data is investigated using 51 crystal structures, with the aim of allowing increasingly complex crystal structures to be solved more easily. The findings confirm that conformational information derived from the Cambridge Structural Database is indeed of value, considerably increasing the chances of obtaining a successful structure determination. Its routine use is therefore encouraged.

Structure of Pigment Yellow 181 dimethylsulfoxide N-methyl-2-pyrrolidone (1:1:1) solvate from XRPD + DFT-D

With only a 2.6 Å resolution laboratory powder diffraction pattern of the θ phase of Pigment Yellow 181 (P.Y. 181) available, crystal-structure solution and Rietveld refinement proved challenging; especially when the crystal structure was shown to be a triclinic dimethylsulfoxide N-methyl-2-pyrrolidone (1:1:1) solvate. The crystal structure, which in principle has 28 possible degrees of freedom, was determined in three stages by a combination of simulated annealing, partial Rietveld refinement with dummy atoms replacing the solvent molecules and further simulated annealing. The θ phase not being of commercial interest, additional experiments were not economically feasible and additional dispersion-corrected density functional theory (DFT-D) calculations were employed to confirm the correctness of the crystal structure. After the correctness of the structure had been ascertained, the bond lengths and valence angles from the DFT-D minimized crystal structure were fed back into the Rietveld refinement as geometrical restraints (`polymorph-dependent restraints') to further improve the details of the crystal structure; the positions of the H atoms were also taken from the DFT-D calculations. The final crystal structure is a layered structure with an elaborate network of hydrogen bonds.

The hybrid big bang–big crunch method for solving crystal structure from powder diffraction data

The big bang–big crunch method is a global optimization approach developed upon the analogy of one of the cosmological theories of the evolution of the universe. It has been suitably combined with a simulated annealing algorithm and used for solving crystal structure from powder diffraction data in direct space. When compared with the traditional simulated annealing method, it provides a significant advance: good solutions are attained in a shorter time. The new method has been implemented in theEXPOpackage. Its successful application is demonstrated with examples of already known structures.

Lithol Red: a systematic structural study on salts of a sulfonated azo pigment

The first systematic series of single-crystal diffraction structures of azo lake pigments is presented (Lithol Red with cations=Mg(II), Ca(II), Sr(II), Ba(II), Na(I) and Cd(II)) and includes the only known structures of non-Ca examples of these pigments. It is shown that these commercially and culturally important species show structural behaviour that can be predicted from a database of structures of related sulfonated azo dyes, a database that was specifically constructed for this purpose. Examples of the successful structural predictions from the prior understanding of the model compounds are that 1) the Mg salt is a solvent-separated ion pair, whereas the heavier alkaline-earth elements Ca, Sr and Ba form contact ion pairs, namely, low-dimensional coordination complexes; 2) all of the Lithol Red anions exist as the hydrazone tautomer and have planar geometries; and 3) the commonly observed packing mode of alternating inorganic layers and organic bilayers is as expected for an ortho-sulfonated azo species with a planar anion geometry. However, the literature database of dye structures has no predictive use for organic solvate structures, such as that of the observed Na Lithol Red DMF solvate. Interestingly, the Cd salt is isostructural with the Mg salt and not with the Ca salt. It is also observed that linked eight-membered [MOSO](2) rings are the basic coordination motif for all of the known structures of Ca, Sr and Ba salts of sulfonated azo pigments in which competing carboxylate groups are absent.

2-[2-(2-Carboxyphenyl)hydrazinylidene]-3-oxo-N-phenylbutyramide

In the title compound, C₁₇H₁₅N₃O₄, the mol­ecule is in the keto–hydrazone form. Intra­molecular N—H⋯O hydrogen bonds ensure that the mol­ecule is nearly planar (r.m.s. deviation of non-H atoms is 0.098 Å), with the two benzene rings forming a dihedral angle of 10.04 (2)°. In the crystal, inversion dimers are formed via pairs of O—H⋯O hydrogen bonds involving the –CO₂H groups.

Validation of experimental molecular crystal structures with dispersion-corrected density functional theory calculations

The accuracy of a dispersion-corrected density functional theory method is validated against 241 experimental organic crystal structures from Acta Cryst. Section E.

This paper describes the validation of a dispersion-corrected density functional theory (d-DFT) method for the purpose of assessing the correctness of experimental organic crystal structures and enhancing the information content of purely experimental data. 241 experimental organic crystal structures from the August 2008 issue of Acta Cryst. Section E were energy-minimized in full, including unit-cell parameters. The differences between the experimental and the minimized crystal structures were subjected to statistical analysis. The r.m.s. Cartesian displacement excluding H atoms upon energy minimization with flexible unit-cell parameters is selected as a pertinent indicator of the correctness of a crystal structure. All 241 experimental crystal structures are reproduced very well: the average r.m.s. Cartesian displacement for the 241 crystal structures, including 16 disordered structures, is only 0.095 Å (0.084 Å for the 225 ordered structures). R.m.s. Cartesian displacements above 0.25 Å either indicate incorrect experimental crystal structures or reveal interesting structural features such as exceptionally large temperature effects, incorrectly modelled disorder or symmetry breaking H atoms. After validation, the method is applied to nine examples that are known to be ambiguous or subtly incorrect.