In situ cryocrystallization of diphenyl ether: C-H...pi mediated polymorphic forms

Polymorphism in diphenyl ether has been identified during in situ crystallization via single-crystal X-ray diffraction. Only weak inter- and intramolecular C-H...pi interactions control the packing of the molecules in both crystal forms monoclinic centrosymmetric (P21/n) in form I and orthorhombic noncentrosymmetric (P212121) in form II.     

Molecular conformation and packing of peptide beta hairpins in the solid state: structures of two synthetic octapeptides containing 1-aminocycloalkane-1-carboxylic acid residues at the i+2 position of the beta turn

Peptide beta-hairpin formation is facilitated by centrally positioned D-Pro-Xxx segments. The synthetic peptides Boc-Leu-Phe-Val-D-Pro-Ac(6)c-Leu-Phe-Val-OMe (1) and Boc-Leu-Phe-Val-D-Pro-Ac(8)c-Leu-Phe-Val-OMe (2) were synthesized in order to explore the role of bulky 1-aminocycloalkane-1-carboxylic acid residues (Ac(n)c, where n is the number of carbon atoms in the ring), at the i+2 position of the nucleating beta turn in peptide beta hairpins. Peptides 1 and 2 crystallize in the monoclinic space group P2(1) with two molecules in the asymmetric unit. The crystal structures of 1 and 2 provide conformational parameters for four peptide hairpin molecules. In all cases, the central segments adopts a type II' beta-turn conformation, and three of the four possible cross-strand hydrogen bonds are observed. Fraying of the hairpins at the termini is accompanied by the observation of NHpi interaction between the Leu(1)NH group and Phe(7) aromatic group. Cross strand stabilizing interactions between the facing residues Phe(2) and Phe(7) are suggested by the observed orientation of aromatic rings. Anomalous far-UV CD spectra observed in solution suggest that close proximity of the Phe rings is maintained even in isolated molecules. In both peptides 1 and 2, the asymmetric unit consists of approximately orthogonal hairpins, precluding the formation of a planar beta-sheet arrangement in the solid state. Solvent molecules, one dioxane and one water in 1, three water molecules in 2, mediate peptide association. A comparison of molecular conformation and packing motifs in available beta-hairpin structures permits delineation of common features. The crystal structures of beta-hairpin peptides provide a means of visualizing different modes of beta-sheet packing, which may be relevant in developing models for aggregates of polypeptides implicated in disease situations.     

Prediction of possible crystal structures for C-, H-, N-, O-, and F-containing organic compounds

A procedure is reported for the prediction of dense crystal structures of C-, H-, N-, O-, and F-containing organic compounds in the primitive triclinic, monoclinic, and orthorhombic space groups with Z ≤ 4. The crystal environments of molecules in 242 crystal structures have been analyzed to determine the common coordination sphere pattens. This led to the development of the MOLPAK (MOLecular PAcKing) program, which uses a rigid-body molecular structure probe to build packing arrangements (possible crystal structures) in the various space groups. A MOLPAK search, which involves the investigation of all unique orientations of a central molecule and the construction of the appropriate coordination patterns about the central molecule, provides a 3-D map of minimum unit cell volume as a function of the orientation of the central molecule. MOLPAK uses a repulsion-only potential and a preset threshold to place molecules in contact with each other. The 5–10 smallest volume packing arrangements from a search are subjected to a lattice energy minimization refinement with the WMIN program to yield possible crystal structures. The results are described from the analyses of several known compounds starting with the crystal molecular structures as the MOLPAK search probes in the P1, P2₁, P2₁/c, and P2₁2₁2₁ space groups. In addition, several examples are given in which the search probes were created by AM1 geometry optimization of preliminary molecular models. More extensive data are given in supplementary tables. © 1993 John Wiley & Sons, Inc.     

Morphological evolution of inorganic crystal into zigzag and helical architectures with an exquisite association of polymer: a novel approach for morphological complexity

The morphology of potassium sulfate (K(2)SO(4)) crystals grown in a viscous polymer solution of poly(acrylic acid) (PAA) was remarkably changed from the tilted columnar assembly into zigzag and helical architectures with increasing PAA concentration. The habit modification of orthorhombic K(2)SO(4) with adsorption of PAA molecules on a specified crystal face fundamentally led to the formation of tilted unit crystals. Concurrently with the habit modification, a diffusion-limited condition controlling the assembly of tilted units was achieved in the presence of PAA molecules in the matrix. Various complex morphologies, including zigzag and helical assembly, emerged through the formation of twinned crystals with the variation of the diffusion condition. Understanding the morphogenesis observed in this report would provide a novel approach for sophisticated crystal design by using an exquisite association of organic and inorganic materials.     

On the clathrate structures of syndiotactic poly(m-methylstyrene)

The crystal structures of clathrate forms of syndiotactic poly(m-methylstyrene) containing guest molecules having different steric hindrance (CS₂, benzene and orto-dichlorobenzene) are presented. The structures are all characterized by polymer chains in s (2/1)2 helical conformation and guest molecules packed in an orthorhombic unit cell according to the space group Pcaa. All the presented clathrates belongs to β class indipendently from the dimensions of the guest molecule. In this aspect they differ both from clathrate forms of syndiotactic polystyrene, all belonging to α class, and from clathrate forms of syndiotactic poly(p-methylstyrene) that belong to α or β class according to the steric hindrance of the guest molecule.     

Structural, thermoanalytical and molecular modeling studies on N-(3-hydroxypropyl) 3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-amide and its monohydrates

The synthetic method for preparing N-(3-hydroxypropyl) 3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-amide can lead to formation of at least three different crystal forms - an anhydrous compound and two monohydrates. The structural and thermal properties of these forms have been characterized by 13C-CP/MAS-NMR and IR spectroscopy, thermo- gravimetry, differential scanning calorimetry and by powder and single crystal x-ray crystallography. In addition, theoretical 13C-NMR chemical shift calculations were also performed for the anhydrous compound and for the first monohydrate, starting from single crystal structures and the structures of these species have now been verified. The first monohydrate, C27H47NO4 x H2O, crystallizes in orthorhombic space group P2(1)2(1)2(1) with cell parameters: a = 7.1148(2), b = 18.1775(5), c = 20.1813(6), Z = 4.     

[Co(2,3-tri)(men)Cl][ZnCl4] 体系中三个经式异构体的晶体结构

在[Co(2,3-tri)(men)Cl][ZnCl₄](2,3-tri = N-(2-氨乙基)-1,3-丙二胺;men=N-甲基乙二胺)体系中可能的几何异构体的数目多达二十个,其中经式异构体八个,面式异构体十二个。用单晶 X-射线衍射分析方法解析了三个获得单晶的经式异构体,它们的晶体学参数:(1)m3-[ZnCl₄](monoclinic P2₁/c,a=8.0874(18),b=1     

碱金属硒化物MHgSbSe~3(M=K,Rb, Cs)的晶体结构及其半导体性 质的研究

用有机溶剂热生长技术(SolvothermalTechnique)制备碱金属硒化物MHgSbSe~3(M=K,Rb,Cs),用单晶X射线衍射技术对其进行晶体结构分析,热分析结果表明,在常温(<200℃)下均为稳定的化合物。光学性质测试表明它们是半导体材料,KHgSbSe~3,RbHgSbSe~3,CsHgSbSe~3的禁带宽度依次为1.85eV,1.75eV,1.65eV。     

Solvent-induced polymorphism of three-dimensional hydrogen-bonded networks of hexakis(4-carbamoylphenyl)benzene

The crystal structures for three types of three-dimensional (3-D) hydrogen-bonded networks of hexakis(4-carbamoylphenyl)benzene (1), the network morphologies of which depend greatly on crystallization conditions, have been determined. When this compound is crystallized from hot DMSO, the resulting crystals, 1.12DMSO (orthorhombic, Pca2(1)), showed a 3-D hydrogen-bonded porous network (type A) via 1-D catemer chains as a hydrogen-bonding motif of six primary amide groups. The type A network creates chambers surrounded by six molecules of 1 and channels along the c axis to give the highest porosity among the network polymorphs of 1 investigated here. Crystallization from a boiling mixture of n-PrOH and water gave 1.6n-PrOH (monoclinic, P2(1)/c), which exhibits another type of 3-D hydrogen-bonded porous network (type B) via cyclic dimers as another hydrogen-bonding motif of six primary amide groups. The type B network leads to triangle-like channels along the a axis having a cross section of ca. 9.2 x 9.7 x 9.7 A (including van der Waals radii). The crystal structure of 1.H(2)O (monoclinic, P2(1)/c), which was produced under hydrothermal conditions, showed a nonporous 3-D hydrogen-bonded network chain of amide groups (type C) composed of a mixed hydrogen bonding motif of helical catemer chains/cyclic dimer/catemer. Solvent-induced topological isomerism of these 3-D hydrogen-bonded networks of 1 arises from (i) the guest inclusion ability based on a radially functionalized hexagonal structure of 1, (ii) the correlation between the hydrogen bond donor ability of the syn and anti protons of the primary amide group in host 1 and the hydrogen bond acceptor ability of the oxygen atoms of 1 and guest solvents, and (iii) the polarity of the bulk crystallization solvents.     

New iron(III) phosphate phases: crystal structure and electrochemical and magnetic properties

Two new iron(III) phosphates, FePO(4), have been synthesized from the dehydration of hydrothermally prepared monoclinic and orthorhombic hydrated phosphates FePO(4).2H(2)O. The structures of both hydrates were redetermined from single crystal data. On dehydration, a topotactic reaction takes place with only those bonds associated with the water molecules being broken, so that both FePO(4) phases have essentially the same Fe-P backbone frameworks as the corresponding hydrates. They are, respectively, monoclinic FePO(4), space group P2(1)/n, a= 5.480(1) A, b = 7.480(1) A, c= 8.054(1) A, beta = 95.71(1) degrees, and Z = 4; and orthorhombic FePO(4), space group Pbca, a = 9.171(1) A, 9.456(1) A, c = 8.675(1) A, and Z = 8. Both of these phases are thermally unstable relative to the trigonal quartz-like FePO(4). The electrochemical studies find that the orthorhombic iron phosphate is more active than the monoclinic phase, while both are more active than trigonal FePO(4). Both phases approach Curie-Weiss behavior at room temperature, with the monoclinic phase exhibiting stronger antiferromagnetic interactions due to Fe-O-Fe interactions. The electrochemical and magnetic data are consistent with the structures of these two compounds. The properties of these new iron phosphate structures are compared with other iron phosphate phases.     

Fluoride und Fluorosäuren. IV. Kristallstrukturen von Bortrifluorid und seinen 1:1-Verbindungen mit Wasser und Methanol,Hydroxo- und Methoxotrifluoroborsäure

Fluorides and Fluoro Acids. IV. Crystal Structures of Boron Trifluoride and its 1:1 Compounds with Water and Methanol, Hydroxo- and Methoxotrifluoroboric Acid Solid boron trifluoride displays an enantiotropic phase transition α ? β at ?147°C. A further solid phase, γ-BF₃, is metastable or stable only just below the melting point. Its crystal structure was determined. It is monoclinic with space group P2₁/c, eight molecules in the unit cell and the lattice parameters a = 4.779, b = 14.00, c = 7.430 Å, β = 107.60° at ?131°C. Two independent trigonal planar molecules with a mean B? F bond length of 1.287 Å (1.319 Å after correction for thermal motion) form a three-dimensional packing connection with non-parallel molecular planes across intermolecular B···F contacts of in the average 2.690 Å, by which the boron atoms achieve a total coordination of five fluorine atoms with nearly trigonal bipyramidal geometry. — The crystal structures of hydroxotrifluoroboric acid (BF₃OH₂, monoclinic, P2₁/n, Z = 4, a = 7.641, b = 7.957, c = 4.864 Å, β = 94.80 at ?35°C) and methoxotrifluoroboric acid (BF₃O(CH₃)H, orthorhombic, Pbca, Z = 8, a = 7.054, b = 9.390, c = 11.547 Å at ?40°C) display unlimited three-dimensional and one-dimensional linking, respectively, of the molecules by hydrogen bonds O? H···F.     

Self-assembly of dendronized perylene bisimides into complex helical columns

The synthesis of perylene 3,4:9,10-tetracarboxylic acid bisimides (PBIs) dendronized with first-generation dendrons containing 0 to 4 methylenic units (m) between the imide group and the dendron, (3,4,5)12G1-m-PBI, is reported. Structural analysis of their self-organized arrays by DSC, X-ray diffraction, molecular modeling, and solid-state (1)H NMR was carried out on oriented samples with heating and cooling rates of 20 to 0.2 °C/min. At high temperature, (3,4,5)12G1-m-PBI self-assemble into 2D-hexagonal columnar phases with intracolumnar order. At low temperature, they form orthorhombic (m = 0, 2, 3, 4) and monoclinic (m = 1) columnar arrays with 3D periodicity. The orthorhombic phase has symmetry close to hexagonal. For m = 0, 2, 3, 4 ,they consist of tetramers as basic units. The tetramers contain a pair of two molecules arranged side by side and another pair in the next stratum of the column, turned upside-down and rotated around the column axis at different angles for different m. In contrast, for m = 1, there is only one molecule in each stratum, with a four-strata 2(1) helical repeat. All molecules face up in one column, and down in the second column, of the monoclinic cell. This allows close and extended π-stacking, unlike in the disruptive up-down alteration from the case of m = 0, 2, 3, 4. Most of the 3D structures were observed only by cooling at rates of 1 °C/min or less. This complex helical self-assembly is representative for other classes of dendronized PBIs investigated for organic electronics and solar cells.     

Thermodynamic Properties of Polymorphs of Fluorosulfate Based Cathode Materials with Exchangeable Potassium Ions

FeSO₄F‐based frameworks have recently emerged as attractive candidates for alkali insertion electrodes. Mainly owing to their rich crystal chemistry, they offer a variety of new host structures with different electrochemical performances and physical properties. In this paper we report the thermodynamic stability of two such K‐based “FeSO₄F” host structures based on direct solution calorimetric measurements. KFeSO₄F has been reported to crystallize in two different polymorphic modifications—monoclinic and orthorhombic. The obtained enthalpies of formation from binary components (KF plus FeSO₄) are negative for both polymorphs, indicating that they are thermodynamically stable at room temperature, which is very promising for the future exploration of sulfate based cathode materials. Our measurements show that the low‐temperature monoclinic polymorph is enthalpically more stable than the orthorhombic phase by ≈10 kJ mol^?1, which is consistent with the preferential formation of monoclinic KFeSO₄F at low temperature. Furthermore, observed phase transformations and difficulties in the synthesis process can be explained based on the obtained calorimetric results. The KMnSO₄F orthorhombic phase is more stable than both polymorphs of KFeSO₄F.     

Crystallization and Preliminary Crystallographic Analysis of β-Trichosanthin, an Isoform of Trichosanthin from the Root Tuber of Trichosanthe kirilowii

β-Trichosanthin, a type 1 ribosome-inactivating protein (RIP) isolated from the root tuber of Trichosanthe kirilowii Maxim, is an isoform of trichosanthin. Here we report its crystal- lization in two crystal forms using the hanging-drop vapor-diffusion method. The form A and form B crystals belong to the orthorhombic space group P212121 and monoclinic space group P21, respectively. X-ray data have been collected to 1.6 and 1.2 (A) resolution for form A and form B crystals, respectively, using a synchrotron source.     

Four stereoisomers of the novel μ‐opioid receptor agonist tapentadol hydrochloride

The crystal and molecular structures of four stereoisomers of tapentadol hydrochloride [systematic name: 3‐(3‐hydroxyphenyl)‐N,N,2‐trimethylpentan‐1‐aminium chloride], C₁₄H₂₄NO⁺·Cl⁻, a novel analgesic agent, have been determined by X‐ray crystal structure analysis. Resolution of the isomers was carried out by reverse‐phase and chiral high‐performance liquid chromatographic (HPLC) methods. Stereoisomers (I) and (II) crystallize in the monoclinic space group P2₁, each with two tapentadol cations and two chloride anions in the asymmetric unit, while stereoisomers (III) and (IV) crystallize in the orthorhombic space group P2₁2₁2₁, with one tapentadol cation and one chloride anion in the asymmetric unit. The absolute configurations of the four enantiomers were determined unambiguously by X‐ray crystallography. The crystal structures reveal the stereochemistries at the 3‐ethyl and 2‐methyl groups to be R,R, S,S, S,R and R,S in stereoisomers (I)–(IV), respectively. The ethyl and aminopropyl groups adopt different orientations with respect to the phenol ring for (I) and (IV). In all four structures, the chloride ions take part in N—H...Cl and O—H...Cl hydrogen bonds with the tapentadol molecules, resulting in one‐dimensional helical chains in the crystal packing in each case.     

Three-dimensional open-framework cobalt(II) phosphates by novel routes

Two new three-dimensional open-framework cobalt phosphates, [C2N2H10]2[Co4(PO4)4]H2O, I, and [C4N3H16]3-[Co6(PO4)5(HPO4)3]H2O, II, have been prepared by the reaction of amine phosphates with Co2+ salts. I could also be prepared by the reaction of the cobalt tris amine complex with H3PO4. The crystal data for I and II are as follows: phosphate I, orthorhombic, space group P2(1)2(1)2(1) (no. 19), a = 10.277 (1) A, b = 10.302 (1) A, c = 18.836 (1) A, V = 1994.2 (2) A3, Z = 4; phosphate II, monoclinic, space group P2(1)/c (No. 14), a = 31.950 (1) A, b = 8.360 (1) A, c = 15.920 (1) A, beta = 96.6 (1) degrees V = 4223.4 (2) A3, Z = 4. The structures of both I and II are constructed from alternating CoO4 and PO4 tetrahedra. The connectivity leads to the formation of eight-membered channels in all the crystallographic directions resembling the aluminosilicate zeolite, merlinoite in the case of I and to a rather large, one-dimensional 16-membered channel in II. Strong hydrogen-bond interactions involving the amine and framework oxygen are present in both I and II.     

Studies on structures of some platinum complexes with 1,1-cyclopropanedicarboxylate

The crystal structures of [Pt(NH3)2CPrDCA].H2O (I), [Pt(CH3NH2)2CPrDCA] (II), and [Pt(dmbn) CPrDCA].2.5H2O (III) (where CPrDCA is 1,1-cyclopropanedicarboxylate; dmbn is 2,3-dimethyl-2,3-butyldiamine) are determined. Compound I crystallizes in the orthorhombic space group Pnma with the cell dimensions: a = 6.517(2), b = 9.709(3), c = 14.205(5) A, Z = 4, R = 0.058. Compound II is monoclinic with space group P2(1)/n, a = 9.648(3), b = 8.720(2), c = 12.770(4) A, beta = 107.12(2), Z = 4, R = 0.059. Compound III belongs to the monoclinic system space group P2(1)/m with the cell dimensions: a = 6.494(1), b = 19.638(3), c = 6.606(1)A, beta = 94.44(1), Z = 2, R = 0.038. Electronic structures of the complexes are studied and the correlation between structure of the amine ligands and biological activity of the complexes is explored.     

Study on the bile salt, sodium scymnol sulfate, from Rhizoprionodon acutus. II. The structures of scymnol, anhydroscymnol and sodium scymnol sulfate.

The crystal structures of anhydroscymnol (I) and scymnol (II), which were prepared from sodium scymnol sulfate (III) isolated from the bile of Rhizoprionodon acutus, have been determined by means of X-ray diffraction analyses. The crystals of I are orthorhombic, space group P2(1)2(1)2(1) with Z = 4; unit-cell dimensions: a = 13.562(2), b = 21.636(2), c = 8.735(2) A; II orthorhombic, space group P2(1)2(1)2, with Z = 4; unit-cell dimensions a = 18.553(2), b = 19.887(2), c = 7.986(2) A. Both structures, (24R,25S)-(+)-24,26-epoxy-5 beta-cholestane-3 alpha,7 alpha,12 alpha,27-tetrol (I) and (24R)-(+)-5 beta-cholestane-3 alpha,7 alpha,12 alpha,24,26,27-hexol (II), were solved from diffractometric data by direct methods and refined by least-squares calculations to R = 0.073 (I) and R = 0.062 (II) (2044 (I) and 2250 (II) observed independent significant reflections (I greater than 3 sigma(I)), respectively. All the hydroxyl groups of both compounds are involved in a hydrogen-bonding network. The structure of III was determined to be (24R,25S)-(+)-3 alpha,7 alpha,12 alpha,24,26-pentahydroxy-5 beta-cholestan-27-yl sodium sulfate, based on the chemical data that alkaline degradation of III with aqueous potassium hydroxide gives only I.     

Isostructurality, polymorphism and mechanical properties of some hexahalogenated benzenes: the nature of halogen...halogen interactions

The nature of intermolecular interactions between halogen atoms, X...X (X = Cl, Br, I), continues to be of topical interest because these interactions may be used as design elements in crystal engineering. Hexahalogenated benzenes (C6Cl(6-n)Br(n), C6Cl(6-n)I(n), C6Br(6-n)I(n)) crystallise in two main packing modes, which take the monoclinic space group P2(1)/n and the triclinic space group P1. The former, which is isostructural to C6Cl6, is more common. For molecules that lack inversion symmetry, adoption of this monoclinic structure would necessarily lead to crystallographic disorder. In C6Cl6, the planar molecules form Cl...Cl contacts and also pi...pi stacking interactions. When crystals of C6Cl6 are compressed mechanically along their needle length, that is, [010], a bending deformation takes place, because of the stronger interactions in the stacking direction. Further compression propagates consecutively in a snakelike motion through the crystal, similar to what has been suggested for the motion of dislocations. The bending of C6Cl6 crystals is related to the weakness of the Cl...Cl interactions compared with the stronger pi...pi stacking interactions. The triclinic packing is less common and is restricted to molecules that have a symmetrical (1,3,5- and 2,4,6-) halogen substitution pattern. This packing type is characterised by specific, polarisation-induced X...X interactions that result in threefold-symmetrical X3 synthons, especially when X = I; this leads to a layered pseudohexagonal structure in which successive planar layers are inversion related and stacked so that bumps in one layer fit into the hollows of the next in a space-filling manner. The triclinic crystals shear on application of a mechanical stress only along the plane of deformation. This shearing arises from the sliding of layers against one another. Nonspecificity of the weak interlayer interactions here is demonstrated by the structure of twinned crystals of these compounds. One of the compounds studied (1,3,5-tribromo-2,4,6-triiodobenzene) is dimorphic, adopting both the monoclinic and triclinic structures, and the reasons for polymorphism are suggested. To summarise, both chemical and geometrical models need to be considered for X...X interactions in hexahalogenated benzenes. The X...X interactions in the monoclinic group are nonspecific, whereas in the triclinic group some X...X interactions are anisotropic, chemically specific and crystal-structure directing.     

CRYSTAL STRUCTURE OF BID[N-t-BUTYLBUTEN-2-YLIDENE] DICHLOROPALLADIUM(II)

<正> The title compound, C15H30N2PdCl2 (Mr=427.73), crystallizes in two kinds of crystal forms I and II.I : monoclinic, P21/c, a = 8.234(1), b = 13.702(3), c = 8.939(2) A, β = 93.90(1)°, V = 1010.55 A3, DC = 1.407g/cm3, R = 0.032 for 2098 observed reflections.II: triclinic, Pl, a=8.179(1), b=8.182(1). c=8.231(2) A, α=91.89(1)°, β=91.90(2)°, α=113.80(1)°, V =503.09A3, DC =1.413 g/cm3, R = 0.036 for 1770 observed reflections.The molecules in both crystals I and II possess the identical configurations but there are two orientations of molecules in the crystal II.