metal-organic compounds
Open access
The asymmetric unit of the title compound, poly[(μ4-{[bis(hydrogen phosphonatomethyl)azaniumyl]methyl}phosphonato)lanthanum(III)], [La(C3H9NO9P3)]n, comprises an La3+ center and a H3nmp3− anion (where H3nmp3− is a residue of partially deprotonated nitrilotris(methylenephosphonic acid), namely {[bis(hydrogen phosphonatomethyl)azaniumyl]methyl}phosphonate). This study concerns a structural redetermination using single-crystal X-ray diffraction data, collected at the low temperature of 180 K, of a recently investigated material whose structural details have been proposed from powder X-ray diffraction studies [Silva et al. (2011). J. Am. Chem. Soc. 133, 15120–15138]. The main difference between the two models rests on the position of the H atoms. While two H atoms were modeled as attached to the same phosphonate group in the powder determination, in the current model, the same H atoms are instead distributed among two of these groups. The sample studied was an inversion twin.
organic compounds
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The asymmetric unit of the title compound, C4H5N7, comprises two independent but virtually superimposable molecules. Each molecule is planar with the dihedral angles between the five-membered rings being 2.8 (3) and 2.1 (3)°. The crystal structure is formed by an extensive network of relatively strong N—HN hydrogen-bond interactions. Individual molecules are arranged into supramolecular zigzag chains running parallel to [001] by way of the strongest N—HN interactions. Adjacent chains are interconnected by rather long (DA distances range from ca 3.00 to 3.03 Å) but highly directional (interaction angles above ca 173°) hydrogen bonds forming a supramolecular layer in the bc plane.
organic compounds
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The title compound, C23H19N, was obtained unexpectedly from the reaction of [Eu(nta)3(PzPy)] {Hnta = 1-(2-naphthoyl)-3,3,3-trifluoroacetone and PzPy = 2-[3(5)-pyrazolyl]pyridine} with 1-naphthylmethylamine. The 1- and 2-naphthyl groups are essentially planar [r.m.s. deviations of 0.007 and 0.011 Å, respectively] and subtend angles of 38.69 (11) and 16.50 (11)°, respectively, with the central CH3—C=N—CH2 unit, which is also almost planar [r.m.s. deviation = 0.002 Å]. In the crystal, the molecules are disposed in zigzag-type fashion, forming layers perpendicular to [100]. Weak supramolecular C—Hπ interactions contribute to the packing forces.
organic compounds
Open access
The title compound, C15H22N2O3, was obtained as a by-product of oxidative cleavage of 1,3-dicyclohexyl-(3-oxo-2,3-dihydrobenzofuran-2-yl)imidazolidine-2,4-dione. Herein, we report the crystal structure of a second polymorph, which was obtained by crystallization from an ethanol solution at 253 K, instead of slow evaporation of the same solvent at room temperature. While the first polymorph [Talhi et al. (2011). Acta Cryst. E67, o3243] crystallized in the non-centrosymmetric space group P212121, this second polymorph crystallizes in the centrosymmetric space group P21/n. Compared to the first polymorph, in the crystal no C=OC=O interactions were found (CO intermolecular distance longer than 3.15 Å) and instead, close packing of individual molecular units is mediated by C—Hπ and weak C—HO interactions.