Sándor L. Bekö

X-ray powder diffraction, solid-state NMR and dispersion-corrected DFT calculations to investigate the solid-state structure of 2-ammonio-5-chloro-4-methylbenzenesulfonate

Abstract The title compound, also called CLT acid, is an industrial intermediate in the synthesis of laked red azo pigments for newspaper printing. Solid-state NMR and IR experiments revealed the compound to exist as the zwitterionic tautomer in the solid state. The crystal structure was solved from X-ray powder diffraction data by means of real-space methods using the program DASH 3.1. Subsequently the structure was refined by the Rietveld method with TOPAS 4.1. The zwitterionic tautomer gave better confidence values than the non-zwitterionic tautomer. Finally the structure was confirmed by dispersion-corrected density-functional calculations. The compound crystallises in the monoclinic space group Ia, Z = 4 with a = 5.49809(7) Å, b = 32.8051(5) Å, c = 4.92423(7) Å, β = 93.5011(7)° and V = 886.50(2) Å3. The molecules form a herringbone pattern with a double layer structure consisting of alternating polar and non-polar layers. Within the polar layers hydrogen bonds and ionic interactions are dominant, whereas the fragments in the non-polar layers are connected by van der Waals interactions.

Crystal Structures of the Hydration States of Pigment Red 57:1

Today, most journals and newspapers are printed with Pigment Red 57:1 (P.R.57:1, 1). This is true for scientific journals like Angewandte Chemie and Zeitschrift f r Kristallographie as well as for newspapers such as The New York Times, The Sun, Bild, El Pa s, La Repubblica, Le Monde, and Shanghai Daily. P.R.57:1 is the most important organic red pigment with a production of more than 50 000 tons per year and an annual sales volume of more than 200 million Euro. 3] In printing ink the pigment is not dissolved, but finely dispersed. Consequently the solid-state properties are maintained. Most pigments, including P.R.57:1, occur in different crystal phases with different colors. Although P.R.57:1 has been industrially produced for more than 100 years, the crystal structures of P.R.57:1 have never been determined. 6] Here we report the crystal structures of three crystal phases of P.R.57:1 (Scheme 1). The compound is industrially synthesized in water by azo coupling and subsequent laking with CaCl2 (see Scheme 2). In the solid state all commercial “azo pigments” do not contain an azo group but adopt the tautomeric hydrazone form (Scheme 2). Thus the name “hydrazone pigments” is more

Nimustine hydrochloride: the first crystal structure determination of a 2-chloroethyl-N-nitrosourea hydrochloride derivative by X-ray powder diffraction and solid-state NMR.

Nimustine hydrochloride [systematic name: 4-amino-5-({[N-(2-chloroethyl)-N-nitrosocarbamoyl]amino}methyl)-2-methylpyrimidin-1-ium chloride], C(9)H(14)ClN(6)O(2)(+)·Cl(-), is a prodrug of CENU (chloroethylnitrosourea) and is used as a cytostatic agent in cancer therapy. Its crystal structure was determined from laboratory X-ray powder diffraction data. The protonation at an N atom of the pyrimidine ring was established by solid-state NMR spectroscopy.

Determination of crystal structures and tautomeric states of 2-ammoniobenzenesulfonates by laboratory X-ray powder diffraction

Abstract The crystal structures of 4-chloro-5-methyl-2-ammoniobenzenesulfonate and of the corresponding derivatives 4,5-dimethyl- and 4,5-dichloro-2-ammoniobenzenesulfonates have been determined from laboratory X-ray powder diffraction data. The tautomeric state of all three compounds could also be unequivocally determined from laboratory data, using careful Rietveld refinements. The tautomeric state was confirmed by IR spectroscopy. The compounds are neither isostructural to each other nor to the 5-chloro-4-methyl derivate, despite the similar size of the chloro and methyl substituents. The influence of the chloro and methyl substituents on the packing and on the thermal stability is demonstrated. All crystal structures were confirmed by dispersion-corrected DFT calculations. For the 4-chloro-5-methyl and the 4,5-dichloro derivatives the DFT calculations indicated that the observed polymorph should not be the thermodynamical one. However, no other polymorphs could be found in experimental polymorph screening, even using seeding with the corresponding isostructural phases. Obviously the DFT methods need further improvements.

One-dimensional zinc(II) fumarate coordination polymers

A new procedure developed for the synthesis and crystallization of various zinc(II) fumarate hydrate coordination polymers is described. In the first step, anhydrous Zn(II) fumarate, [Zn(C4H2O4)] (1), is synthesized from Zn(II) acetate and fumaric acid in methanol. Subsequently, this product is used as a starting material for growing small crystals of bis–aqua Zn(II) fumarate, [Zn(H2O)2(C4H2O4)] (2), triaqua Zn(II) fumarate monohydrate, [Zn(H2O)3(C4H2O4)]·H2O (3), tetraaqua Zn(II) fumarate, [Zn(H2O)4(C4H2O4)] (4), and tetraaqua Zn(II) fumarate monohydrate, [Zn(H2O)4(C4H2O4)]·H2O (5). All structures were determined or redetermined by X-ray structure analyses. The hitherto unknown compound 3 exhibits a zig-zag chain structure with five-coordinate Zn(II) ions. Graphical Abstract

Tizanidine and tizanidine hydrochloride: on the correct tautomeric form of tizanidine.

A crystallization series of tizanidine hydrochloride, used as a muscle relaxant for spasticity acting centrally as an α(2)-adrenergic agonist, yielded single crystals of the free base and the hydrochloride salt. The crystal structures of tizanidine [systematic name: 5-chloro-N-(imidazolidin-2-ylidene)-2,1,3-benzothiadiazol-4-amine], C(9)H(8)ClN(5)S, (I), and tizanidine hydrochloride {systematic name: 2-[(5-chloro-2,1,3-benzothiadiazol-4-yl)amino]imidazolidinium chloride}, C(9)H(9)ClN(5)S(+)·Cl(-), (II), have been determined. Tizanidine crystallizes with two almost identical molecules in the asymmetric unit (r.m.s. deviation = 0.179 Å for all non-H atoms). The molecules are connected by N-H···N hydrogen bonds forming chains running along [2 ̅11]. The present structure determination corrects the structure determination of tizanidine by John et al. [Acta Cryst. (2011), E67, o838-o839], which shows an incorrect tautomeric form. Tizanidine does not crystallize as the usually drawn 2-amino-imidazoline tautomer, but as the 2-imino-imidazolidine tautomer. This tautomer is present in solution as well, as shown by (1)H NMR analysis. In tizanidine hydrochloride, cations and anions are connected by N-H···Cl hydrogen bonds to form layers parallel to (100).

4,4'-{Diazenediylbis[(1,4-phenylene)bis(carbonyloxy)]}bis(2,2,6,6-tetramethylpiperidinyloxidanyl): the first crystal structure determination from powder data of a nitroxide radical.

The title compound, C32H42N4O6, is a novel nitroxide radical used for pulsed electron-electron double resonance (PELDOR) spectroscopy. Its crystal structure was determined from laboratory X-ray powder diffraction data. The attractive forces between the molecules in the crystal structure are mainly of dispersive nature. A special interaction of the nitroxide radicals was not observed.

Crystal Structures of Pigment Red 57:1

Zeitschrift für Kristallographie, Angewandte Chemie, The New York Times, The Sun, El Pais, La Republica, Le Monde, Shanghai Daily, and many more journals and newspapers are printed with Pigment Red 57:1. P.R.57:1 (C18H12CaN2O6S ∙ n H2O, n = 0,1,3) is the most important organic red pigment with a production of more than 50,000 tons per year and an annual sales volume of more than 200 million Euro.[1] In printing ink the pigment is not dissolved, but finely dispersed. Consequently its solid-state properties are maintained. Like most pigments, P.R.57:1 occurs in different crystal phases with different colours. Upon synthesis a trihydrate is formed. Drying at 50 °C generates a monohydrate with magenta shade, which is used for printing inks. The monohydrate is thermally stable up to temperatures higher than 190 °C before it releases water to yield a hygroscopic anhydrous phase with dull dark magenta shade. For all three phases the growth of single crystals is impeded by the low solubility of the pigment in most media. The crystal structures of all three forms were determined from in-house X-ray powder data.[2] The structures were solved by real-space methods with simulated annealing. Subsequently a Rietveld refinement with restraints on bond lengths, bond angles and planar groups was performed. All three phases crystallize in space-group type P21/c, Z = 4. The trihydrate and the monohydrate show eightfold coordination of the Ca ions, the anhydrate a sevenfold one. Apparently the increasing anion-cation interactions lead to the observed colour shift. The arrangement of cations and anions is similar in all three forms. The crystal structures exhibit double layers, one polar, one nonpolar. The polar layer consists of water molecules, calcium ions, sulfonate, keto and carboxylate groups, held together mostly by hydrogen bonds and Coulomb interactions. The nonpolar layer contains naphthalene and toluene moieties.

CCDC 855116: Experimental Crystal Structure Determination

Related Article: Sandor L. Beko, Jan W. Bats, Edith Alig and Martin U. Schmidt|2013|J.Chem.Cryst.|43|655|doi:10.1007/s10870-013-0467-1

5′-Deoxy-5-Fluorouridine: Characterisation, Crystal Structure and Molecular Conformations Determined from X-Ray Powder Data

The title compound [systematic name: 1-[(1R,2R,3S,4R)-2,3-dihydroxy-4-methyltetrahydrofuranyl]-5-fluoropyrimidine-2,4(1H,3H)-dione], C9H11FN2O5, is a prodrug of 5-fluorouracil used as a cytostatic in cancer therapy. Its crystal structure was determined from laboratory X-ray powder diffraction data. The compound crystallises in the triclinic space group P1 with two molecules in the asymmetric unit. These symmetrically independent molecules differ in their hydrogen-bond patterns, the pseudorotational angles P of their furanosyl fragments as well as their N-glycosidic torsion angles χ.Graphical AbstractThe crystal structure of 5′-deoxy-5-fluorouridine, 1-[(1R,2R,3S,4R)-2,3-dihydroxy-4-methyltetrahydrofuranyl]-5-fluoropyrimidine-2,4(1H,3H)-dione], C9H11FN2O5, a prodrug of 5-fluorouracil used as a cytostatic in cancer therapy, was determined from laboratory X-ray powder diffraction data. The compound crystallises in the triclinic space group P1 with two symmetrically independent molecules differing in their hydrogen-bond patterns, the pseudorotational angles P of their furanosyl fragments as well as their N-glycosidic torsion angles χ.