Acta Crystallographica Section C Structural Chemistry最新文献

The incommensurately modulated structure of (2S,3S)-2-amino-3-hydroxy-3-methyl-4-phenoxybutanoic acid dihydrate (C₁₁H₁₅NO₄·2H₂O or I·2H₂O) is described in the (3+1)-dimensional superspace group P2₁2₁2₁(0β0)000 (β = 0.357). The loss of the three-dimensional periodicity is ascribed to the occupational modulation of one positionally disordered solvent water molecule, where the two positions are related by a small translation [ca 0.666 (9) Å] and ∼168 (5)° rotation about one of its O-H bonds, with an average 0.624 (3):0.376 (3) occupancy ratio. The occupational modulation of this molecule arises due to the competition between the different hydrogen-bonding motifs associated with each position. The structure can be very well refined in the average approximation (all satellite reflections disregarded) in the space group P2₁2₁2₁, with the water molecule refined as disordered over two positions in a 0.625 (16):0.375 (16) ratio. The refinement in the commensurate threefold supercell approximation in the space group P112₁ is also of high quality, with the six corresponding water molecules exhibiting three different occupancy ratios averaging 0.635:0.365.

The synthesis and structural characterization of four novel supramolecular hydrogen-bonded arrangements based on self-assembly from molecular `[Cu(2,2'-biimidazole)]' modules and malonate anions are presented, namely, tetrakis(2,2'-biimidazole)di-μ-chlorido-dimalonatotricopper(II) pentahydrate, [Cu₃(C₃H₂O₄)₂Cl₂(C₆H₆N₄)₄]·5H₂O or [Cu(H₂biim)₂(μ-Cl)Cu_0.5(mal)]₂·5H₂O, aqua(2,2'-biimidazole)malonatocopper(II) dihydrate, [Cu(C₃H₂O₄)(C₆H₆N₄)(H₂O)]·2H₂O or [Cu(H₂biim)(mal)(H₂O)]·2H₂O, bis[aquabis(2,2'-biimidazole)copper(II)] dimalonatodiperchloratocopper(II) 2.2-hydrate, [Cu(C₆H₆N₄)₂(H₂O)]₂[Cu(C₃H₂O₄)(ClO₄)₂]·2.2H₂O or [Cu(H₂biim)₂(H₂O)]₂[Cu(mal)₂(ClO₄)₂]·2.2H₂O, and bis(2,2'-biimidazole)copper(II) bis[bis(2,2'-biimidazole)(2-carboxyacetato)malonatocopper(II)] tridecahydrate, [Cu(C₆H₆N₄)₂][Cu(C₃H₂O₄)(C₃H₃O₄)(C₆H₆N₄)₂]·13H₂O or [Cu(H₂biim)₂][Cu(H₂biim)₂(Hmal)(mal)]₂·13H₂O. These assemblies are characterized by self-complementary donor-acceptor molecular interactions, demonstrating a recurrent and distinctive pattern of hydrogen-bonding preferences among the carboxylate, carboxylic acid and N-H groups of the coordinated 2,2'-biimidazole and malonate ligands. Additionally, coordination of the carboxylate group with the metallic centre helps sustain remarkable supramolecular assemblies, such as layers, helices, double helix columns or 3D channeled architectures, including mixed-metal complexes, into a single structure.

It is well known that Hirshfeld surfaces provide an easy and straightforward way of analysing intermolecular interactions in the crystal environment. The use of atomic Hirshfeld surfaces has also demonstrated that such surfaces carry information related to chemical bonds which allow a deeper evaluation of the structures. Here we briefly summarize the approach of atomic Hirshfeld surfaces while further evaluating the kind of information that can be retrieved from them. We show that the analysis of the metal-centre Hirshfeld surfaces from structures refined via Hirshfeld Atom Refinement (HAR) allow accurate evaluation of contacts of type M...H, and that such contacts can be related to the overall shape of the surfaces. The compounds analysed were tetraaquabis(3-carboxypropionato)metal(II), [M(C₄H₃O₄)₂(H₂O)₄], for metal(II)/M = manganese/Mn, cobalt/Co, nickel/Ni and zinc/Zn. We also evaluate the sensitivity of the surfaces by an investigation of seemingly flat surfaces through analysis of the curvature functions in the direction of C-C bonds. The obtained values not only demonstrate variations in curvature but also show a correlation with the hybridization of the C atoms involved in the bond.

The reaction of titanium(IV) chloride with sodium hexafluoroisopropoxide, carried out in hexafluoroisopropanol, produces titanium(IV) hexafluoroisopropoxide, which is a liquid at room temperature. Recrystallization from coordinating solvents, such as acetonitrile or tetrahydrofuran, results in the formation of bis-solvate complexes. These compounds are of interest as possible Ziegler-Natta polymerization catalysts. The acetonitrile complex had been structurally characterized previously and adopts a distorted octahedral structure in which the nitrile ligands adopt a cis configuration, with nitrogen lone pairs coordinated to the metal. The low-melting tetrahydrofuran complex has not provided crystals suitable for single-crystal X-ray analysis. However, the structure of chloridotris(hexafluoroisopropoxido-κO)bis(tetrahydrofuran-κO)titanium(IV), [Ti(C₃HF₆O)₃Cl(C₄H₈O)₂], has been obtained and adopts a distorted octahedral coordination geometry, with a facial arrangement of the alkoxide ligands and adjacent tetrahydrofuran ligands, coordinated by way of metal-oxygen polar coordinate interactions.

The structures of a series of 2:1 cocrystals formed between 4-(dimethylamino)pyridine and each of 1,2,4,5-tetrachloro-3,6-diiodobenzene, 2C₇H₁₀N₂·C₆Cl₄I₂, 1,2,4,5-tetrabromo-3,6-diiodobenzene, 2C₇H₁₀N₂·C₆Br₄I₂, 1-bromo-4-iodo-2,3,5,6-tetrafluorobenzene, 2C₇H₁₀N₂·C₆BrF₄I, and 1,2-dibromo-4,5-difluoro-3,6-diiodobenzene, 2C₇H₁₀N₂·C₆Br₂F₂I₂, are reported. In all five structures, the core halogen-bonded 2:1 trimolecular units have geometrically similar parameters, with the central halogen-bond donor flanked by two pyridine halogen-bond acceptors twisted with respect to the central halogen-bond donor at angles ranging from 76 to 86°. The I...N halogen-bond separations are all short, ranging from 73.3 to 76.7% of the sum of the van der Waals radii, while the C-I...N bond angles are essentially linear. The Br...N halogen-bond separation in the cocrystal formed with 1-bromo-4-iodo-2,3,5,6-tetrafluorobenzene is 80.4% of the sum of the van der Waals radii. Subtle differences in the crystal packings are attributed to the role of secondary C-H...π and weak π-type interactions with chloro and bromo substituents. The cocrystals 2C₇H₁₀N₂·C₆Cl₄I₂ and 2C₇H₁₀N₂·C₆Br₄I₂ are isomorphous.

The crystal structures of two coordination compounds, (acetato-κO)(2,2'-bipyridine-κ²N,N')(1,10-phenanthroline-κ²N,N')copper(II) acetate hexahydrate, [Cu(C₂H₃O₂)(C₁₀H₈N₂)(C₁₂H₈N₂)](C₂H₃O₂)·6H₂O or [Cu(bipy)(phen)Ac]Ac·6H₂O, and (acetato-κO)bis(2,2'-bipyridine-κ²N,N')copper(II) acetate-acetic acid-water (1/1/3), [Cu(C₂H₃O₂)(C₁₀H₈N₂)₂](C₂H₃O₂)·C₂H₄O₂·3H₂O or [Cu(bipy)₂Ac]Ac·HAc·3H₂O, are reported and compared with the previously published structure of [Cu(phen)₂Ac]Ac·7H₂O (phen is 1,10-phenanthroline, bipy for 2,2'-bipyridine, ac is acetate and Hac is acetic acid). The geometry around the metal centre is pentacoordinated, but highly distorted in all three cases. The coordination number and the geometric distortion are both discussed in detail, and all complexes belong to the space group P-1. The analysis of the geometric parameters and the Hirshfeld surface properties d_norm and curvedness provide information about the metal-ligand interactions in these complexes and allow comparison with similar systems.

Three 2,4-diarylpyrroles were synthesized starting from 4-nitrobutanones and the crystal structures of two derivatives were analysed. These are 4-(4-methoxyphenyl)-2-(thiophen-2-yl)-1H-pyrrole, C₁₅H₁₃NOS, and 3-(4-bromophenyl)-2-nitroso-5-phenyl-1H-pyrrole, C₁₆H₁₁BrN₂O. Although pyrroles without substituents at the α-position with respect to the N atom are very air sensitive and tend to polymerize, we succeeded in growing an adequate crystal for X-ray diffraction analysis. Further derivatization using sodium nitrite afforded a nitrosyl pyrrole derivative, which crystallized in the triclinic space group P-1 with Z = 6. Thus, herein we report the first crystal structure of a nitrosyl pyrrole. Interestingly, the co-operative hydrogen bonds in this NO-substituted pyrrole lead to a trimeric structure with bifurcated halogen bonds at the ends, forming a two-dimensional (2D) layer with interstitial voids having a radius of 5 Å, similar to some reported macrocyclic porphyrins.

The activation of C-C bonds by transition-metal complexes is of continuing interest and acetonitrile (MeCN) has attracted attention as a cyanide source with comparatively low toxicity for organic cyanation reactions. A diiron end-on μ-η¹:η¹-CN-bridged complex was obtained from a crystallization experiment of an open-chain iron-NHC complex, namely, μ-cyanido-κ²C:N-bis{[(acetonitrile-κN)[3,3'-bis(pyridin-2-yl)-1,1'-(methylidene)bis(benzimidazol-2-ylidene)]iron(II)} tris(hexafluorophosphate), [Fe₂(CN)(C₂H₃N)₂(C₂₅H₁₈N₆)₂](PF₆)₃. The cyanide appears to originate from the MeCN solvent by C-C bond cleavage or through carbon-hydrogen oxidation.

Luminescent Cu^I complexes are an important class of coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The title Cu₂I₂P₂S₂-type binuclear complex, di-μ-iodido-bis[(thiourea-κS)(triphenylphosphine-κP)copper(I)], [Cu₂I₂(CH₄N₂S)₂(C₁₈H₁₅P)₂], conventionally abbreviated as Cu₂I₂TPP₂TU₂, where TPP and TU represent triphenylphosphine and thiourea, respectively, is described. In this complex, each Cu^I atom adopts a CuI₂PS four-coordination mode and pairs of atoms are connected to each other by two μ₂-I ligands to form a centrosymmetric binuclear cluster. It was also found that the paper-based film of this complex exhibited obvious luminescence light-up sensing for pyridine and 4-methylpyridine.

During the course of exploring crystallization conditions in generating metal-organic frameworks (MOFs) for use in the crystalline sponge method, two discrete metal-organic complexes, namely, aqua[2,4,6-tris(pyridin-4-yl)-1,3,5-triazine]zinc(II) bromide, [Zn(C₁₈H₁₂N₆)(H₂O)]Br₂, and aqua[2,4,6-tris(pyridin-4-yl)-1,3,5-triazine]zinc(II) chloride, [Zn(C₁₈H₁₂N₆)(H₂O)]Cl₂, were encountered. Structures in the orthorhombic space group Pnma (No. 62) for the bromide congener at 299 K and the chloride congener at 100 K were obtained. A phase transition for the bromide congener occurred upon cooling from 299 to 100 K, yielding a crystal polymorph with four domains that exhibits monoclinic P2₁/m space-group symmetry (No. 11), which arises from conformational changes. The main intramolecular contacts that contribute to the crystal packing in all observed structures are H...H, Halide...H/H...Halide, C...H/H...C, and N...H/H...N. Intramolecular hydrogen bonding between the Zn-bound water and non-Zn-bound pyridyl N atoms is a prominent feature within the three-dimensional networks. Aromatic π-stacking between the non-Zn-bound pyridine rings and contacts involving the halide ligands further stabilize the crystal packing.