The crystal structure of 3-methyluracil from X-ray powder diffraction data

The crystal structure of 3-methyluracil has been determined ab initio by conventional monochromatic X-ray powder diffraction data. The crystal data are: orthorombic, a=6.6294(1), b=13.1816(3), c=6.53938(9) (Å), V=571.45(3) (ų), space group Pbnm, Z=8. The structure was solved by direct methods and the final Rietveld refinement converged to R_p=0.0398, R_wp=0.0528, R_Bragg=0.0294. The crystal structure exhibits endless chains of planar molecules, connected via head-to-tail N-H?O hydrogen bonds.     

Crystal structure and phase transitions in perovskite-like C(NH2)3SnCl3

X-ray single-crystal diffraction, high-temperature powder diffraction and differential thermal analysis at ambient and high pressure have been employed to study the crystal structure and phase transitions of guanidinium trichlorostannate, C(NH₂)₃SnCl₃. At 295 K the crystal structure is orthorhombic, space group Pbca, Z=8, a=7.7506(2) Å, b=12.0958(4) Å and c=17.8049(6) Å, solved from single-crystal data. It is perovskite-like with distorted corner-linked SnCl₆ octahedra and with ordered guanidinium cations in the distorted cuboctahedral voids. At 400 K the structure shows a first-order order-disorder phase transition. The space group is changed to Pnma with Z=4, a=12.1552(2) Å, b=8.8590(2) Å and c=8.0175(1) Å, solved from powder diffraction data and showing disordering of the guanidinium cations. At 419 K, the structure shows yet another first-order order-disorder transformation with disordering of the SnCl₃⁻ part. The space group symmetry is maintained as Pnma, with a=12.1786(2) Å, b=8.8642(2) Å and c=8.0821(2) Å. The thermodynamic parameters of these transitions and the p-T phase diagram have been determined and described.     

Crystal structure and conformation of N,N′-bis (3,5-dichlorosalicylidene)-2-hydroxy 1,3 diamino-2-propan

N,N′-bis(3,5-dichlorosalicylidene)-2-hydroxy-1,3-diamino-2-propan (C₁₇H₁₄Cl₄N₂O₃) was synthesized and its crystal structure determined. It crystallizes in the monoclinic space group, C2/c, with a=29.734(8), b=4.541(1), c=14.694(2) Å, β=115.85(2), R(F²)=0.048 for 1704 independent reflections. The title compound has a twofold axis passing through the central C9 atom. The intramolecular hydrogen bond occurs between the pairs of atoms N1 and O1 [2.648(5) Å] and the hydrogen atom is essentially being bonded to the nitrogen atom. There is no intermolecular proximity between molecules. Conformations of the title compound were investigated by semi-empirical quantum mechanical AM1 calculations. The optimized geometry of the molecular structure corresponding to the non-planar conformation is the most stable conformation in the theoretical calculations. The results strongly indicate that the minimum energy conformation is primarily determined by non-bonded steric interactions.     

Cyclam as a Structure-Directing Agent in the Crystallization of Aluminophosphate Open Framework Materials from Fluoride Media

Two aluminofluorophosphates have been synthesized using 1,4,8,11-tetraazacyclotetradecane (cyclam) as a structure-directing agent (SDA). The two materials were synthesized hydrothermally and their structures solved by microcrystal diffraction using synchrotron radiation. In both cases, the SDA has been located crystallographically. The first material, [F, Cyclam]-AlPO-CHA, has the molecular formula Al₆P₆O₂₄F₂.C₁₀N₄H₂₆ and has a framework structure related to the mineral chabazite, with the cyclam molecules occluded within chabazite-like cages (space group P-1, a=9.0993(4) Å, b=9.2232(5) Å, c=9.3929(4) Å, α=77.881(2)^o, β=87.205(1)^o, γ=87.777(1)^o, Z=1, wR(F²)=0.1354, R(F)=0.0487). The second material, [F, Cu-Cyclam]-AlPO-SAS, has the molecular formula Al₈P₈O₃₂F₂.[CuC₁₀N₄H₂₄.2H₂O] and has a framework structure closely related to STA-6 (SAS) zeolite structure type, although the usual tetragonal symmetry has been reduced to monoclinic by the presence of the fluoride ions (space group P2₁/n, a=10.3738(4) Å, b=14.8060(5) Å, c=13.4494(5) Å, β=90.275(1)^o, Z=2, wR(F²)=0.1484, R(F)=0.0524). The cyclam is occluded as a copper complex ordered within the cages of the structure.     

Synthesis and characterization of the mixed ligand coordination polymer CPO-5

The synthesis and crystal structures of a novel coordination polymer and its high-temperature variant are described. The as-synthesized material (CPO-5-as), of composition Zn(4,4′-bipyridine)(4,4′-biphenyldicarboxylate)·3H₂O, crystallizes in the triclinic space group P-1 (No. 2) with a=11.0197(2), b=14.2975(3), c=7.6586(1) Å, α=95.9760(9)°, β=108.026(1)°, γ=91.373(1)° and V=1139.16(4) Å³. CPO-5-as is composed of tetrahedral zinc centers that are connected by the organic linkers to give five independent, interpenetrating diamond networks. In the structure, there is additional space for channels that are filled with three water molecules. These water molecules can be removed, leading to an anhydrous variant at 130^oC. CPO-5-130, of composition Zn(4,4′-bipyridine)(4,4′-biphenyldicarboxylate), crystallizes in the triclinic space group P-1 (No. 2) with a=11.1844(6), b=14.0497(7), c=7.7198(3) Å, α=96.917(2)°, β=109.527(2)°, γ=89.115(3)° and V=1134.6(1) Å³. The structure of the five interpenetrating networks is virtually unchanged after the dehydration resulting in CPO-5-130 being a porous structure with an estimated free volume of 19.8%.     

Synthesis, crystal structures and investigations on the dehydration reaction of the new coordination polymers poly[diaqua-(μ2-squarato-O,O′)-(μ2-4,4′-bipyridine-N,N′)Me(II)] hydrate (Me=Co, Ni, Fe)

The three new isostructural coordination polymers poly[diaqua-(μ₂-squarato-O,O′)-(μ₂-4,4′-bipyridine-N,N′)Me(II)] hydrate (Me=Fe, Co, Ni) were prepared by hydrothermal reaction. All compounds are isostructural and crystallize in the monoclinic space group P2₁/c with 4 formula units in the unit cell (a=18.893 (1) Å, b=11.450 (1) Å, c=8.0985 (4) Å, β=93.032 (5)°, V=1749.5 (2) ų, [Fe(C₄O₄)(C₁₀H₈)(H₂O)₂]·(H₂O)₃; a=18.937 (1) Å, b=11.342 (1) Å, c=8.0545 (5) Å, β=91.83 (1)°, V=1725.3 (2) ų, [Co(C₄O₄)(C₁₀H₈)(H₂O)₂] · (H₂O)₃; a=18.271 (1) Å, b=11.340 (1) Å, c=7.8946 (4) Å, β=90.69 (5)°, V=1633.1 (2) ų, [Ni(C₄O₄)(C₁₀H₈)(H₂O)₂](H₂O)_1.7). In the crystal structures the metal atoms are coordinated by two squarate dianions, two 4,4′-bipyridine ligands and two water molecules. The metal atoms are connected via the squarate dianions and the 4,4′-bipyridine ligands into layers, which interpenetrate forming a three-dimensional coordination network. This arrangement yields channels in which additional water molecules are embedded. Thermoanalytic investigations show that upon heating the channel water is removed in the first step and that the water coordinated to the metal atoms is emitted in the second step. Both steps are fully reversible with the former reaction proceeding via a topotactic reaction. The hydration and dehydration of the compounds are accompanied with a continuous change of the color of the materials. The de- and reintercalation processes were investigated using single crystal structure analysis, X-ray powder diffraction, temperature-dependent X-ray powder diffraction, simultaneous differential thermoanalysis and thermogravimetry coupled to mass spectroscopy, differential scanning calorimetry and time-dependent UV-Vis spectroscopy. The results of the investigations are discussed and compared with those for the previously reported manganese compound.     

The Crystal Structure of Triuranyl Diphosphate Tetrahydrate

The hydrated neutral uranyl phosphate, (UO₂)₃(PO₄)₂(H₂O)₄, was synthesized by hydrothermal methods. Intensity data were collected using MoKα radiation and a CCD-based area detector. The crystal structure was solved by direct methods and refined by full-matrix least-squares techniques to agreement indices wR₂=0.116 for all data, and R1=0.040, calculated for the 2764 unique observed reflections (∣F_o∣≥4σ_F). The compound is orthorhombic, space group Pnma, Z=4, a=7.063(1) Å, b=17.022(3) Å, c=13.172(3) Å, V=1583.5(5) ų. The structure consists of sheets of phosphate tetrahedra and uranyl pentagonal bipyramids, with composition [(UO₂)(PO₄)]⁻ and the uranophane sheet anion topology. The sheets are connected by a uranyl pentagonal bipyramid in the interlayer that shares corners with a phosphate tetrahedron on each of two adjacent sheets, resulting in an open framework with isolated H₂O groups in the larger cavities of the structure.     

Synthesis and Characterization of a New Layered Aluminophosphate [Al3P4O16][(CH3)2NHCH2CH2NH(CH3)2][H3O]

A new layered aluminophosphate, denoted AlPO-CJ12, has been synthesized in the system Al(OPrⁱ)₃-H₃PO₄-tetramethylethylenediamine-triethyleneglycol and its structure solved by single-crystal X-ray diffraction analysis. It is further characterized by X-ray powder diffraction, ICP, TG, DTA, and elemental analyses. The compound has an empirical formula of [Al₃P₄O₁₆][(CH₃)₂NHCH₂CH₂NH(CH₃)₂][H₃O], and crystallizes in the triclinic space group P-1 (No. 2) with a=8.9907(6) Å b=9.8359(6) Å, c=14.5566(8) Å, α=75.872(3)°, β=88.616(3)°, γ=63.404(3)°, Z=2, R₁=0.0451, and wR₂=0.1094. The alternation of tetrahedral AlO₄ and PO₃ (=O) units forms a sheet structure with a 4×6×8 network. The inorganic layers stacked in an AAAA sequence are held together by the protonated organic amine and water molecules. The co-templating role of the water molecules is studied by the calculation of the nonbonding host-guest interaction energies through a computational simulation.     

Synthesis, crystal structure and charge distribution of Na7As11O31: An oxygen-deficient layered sodium arsenate

A new sodium arsenate with layer structure has been synthesized and its crystal structure solved and refined by single-crystal X-ray diffraction. The crystal is trigonal, space group , a=11.199(3) Å, c=5.411(2) Å, V=587.80(3) Å³, Z=1; the refinement converged to R=0.0282 and wR=0.0751 for 590 reflections with (I)>2sigma(I). The structural model gives the formula Na₇As₁₁O₃₂, which would be non-neutral; besides, the structural model is not validated by the charge distribution (CD) analysis, which gives an unsatisfactory agreement on the computed charges of the cations. The CD analysis suggest incomplete (5/6) occupation of the O5 site, which leads to the deficiency of an oxygen atom per unit cell and to formula Na₇As₁₁O₃₁: this new structural model corresponds to a neutral compound, is validated by the CD analysis, and results in better displacement parameters for O5 than its non neutral counterpart. The (001) anionic layers are built up from corner and edge sharing of As1 and As2 distorted octahedra and As3 distorted tetrahedra, the sodium cations playing the role of interlayer cations. The effects of the oxygen deficiency on the crystal structure are discussed.     

Preparation and Double-Helix Icosahedra Structure of δ-Co2Zn15

The first known example of a regular face-sharing icosahedra helix is presented in the novel crystal structure of δ-Co₂Zn₁₅, solved and refined from single-crystal X-ray and neutron powder diffraction data. The compound δ-Co₂Zn₁₅ is also the first example of an intermetallic compound crystallizing in the acentric hexagonal space group P6₂. The parameters from the single crystal refinement are a=11.292(2) Å, c=7.750(1) Å, Z=4, and R_w=0.025.     

The crystal and molecular structure of 2-methoxy-4-hydroxy-5-oxo-benz[f]azepine

Crystals of 2-methoxy-4-hydroxy-5-oxo-benz[f]azepine belong to the orthorhombic space group P2₁2₁2₁, with a = 14·107, b = 16·924, c = 3·982 Å and four molecules per unit cell. The structure was solved by direct methods and refined to an R index of 0·033 using 876 independent terms. The molecular skeleton is planar within ± 0·04 Å and the only atoms lying out of the plane are two hydrogens of the methyl group. Bond alternation is observed in the 7-membered ring indicating little π-electron delocalization. In the crystal structure the hydroxyl group forms a bifurcated hydrogen bond, one branch of which links the molecules into infinite spirals extending down the twofold screw axes parallel to c.     

Synthesis, structure determination, and infrared spectroscopy of (NpO2)2(SO4)(H2O)4: Prevalence of cation-cation interactions and cationic nets in neptunyl sulfate compounds

The compound (NpO₂)₂(SO₄)(H₂O)₄ was synthesized by evaporation of a Np⁵⁺ sulfate solution. The crystal structure was determined using single crystal X-ray diffraction and refined to an R₁=0.0310. (NpO₂)₂(SO₄)(H₂O)₄ crystallizes in triclinic space group P-1, a=8.1102(7) Å, b=8.7506(7) Å, c=16.234(1) Å, α=90.242(2)°, β=92.855(2)°, γ=113.067(2)°, V=1058.3(2) Å³, and Z=2. The structure contains neptunyl pentagonal bipyramids that share vertices through cation-cation interactions to form a sheet or cationic net. The sheet is decorated on each side by vertex sharing with sulfate tetrahedra, and adjacent sheets are linked together through hydrogen bonding. A graphical representation of (NpO₂)₂(SO₄)(H₂O)₄ was constructed to facilitate the structural comparison to similar Np⁵⁺ compounds. The prevalence of the cationic nets in neptunyl sulfate compounds related to the overall stability of the structure is also discussed.     

New binuclear vanadium(III) and (IV) squarate species: synthesis, structure and characterization of [V(OH)(H2O)2(C4O4)]2·2H2O and (NH4)[(VO)2(OH)(C4O4)2(H2O)3]·3H2O

Two new vanadium squarates have been synthesized, characterized by infrared and thermal behavior and their structures determined by single crystal X-ray diffraction. Both structures are made of discrete, binuclear vanadium entity but in 1, [V(OH)(H₂O)₂(C₄O₄)]₂·2H₂O the vanadium atom is trivalent and the entity is neutral while in 2, (NH₄)[(VO)₂(OH)(C₄O₄)₂(H₂O)₃]·3H₂O, the vanadium atom is tetravalent and the entity is negatively charged, balanced by the presence of one ammonium ion. Both molecular anions are bridged by two terminal μ₂ squarate ligands. 1 crystallizes in the triclinic system, space group P-1, with lattice constants a=7.5112(10) Å, b=7.5603(8) Å, c=8.2185(8) Å, α=106.904(8)°, β=94.510(10)°, γ=113.984(9)° while 2 crystallizes in the monoclinic system, space group C2/c, with a=14.9340(15) Å, b=6.4900(9) Å, c=17.9590(19) Å and β=97.927(12)°. From the magnetic point of view, V(III) binuclear species show ferromagnetic interactions at low temperatures. However, no anomalies pointing to magnetic ordering are observed down to 2 K.     

Synthesis, crystal structure, and structural conversion of Ni molybdate hydrate NiMoO4·nH2O

The synthesis and crystal structure of NiMoO₄·nH₂O were investigated. The hydrate crystallized in the triclinic system with space group P−1, Z=4 with unit cell parameters of a=6.7791(2) Å, b=6.8900(2) Å, c=9.2486(2) Å, α=76.681(2)°, β=83.960(2)°, γ=74.218(2)°. Its ideal chemical composition was NiMoO₄·3/4H₂O rather than NiMoO₄·1H₂O. Under hydrothermal conditions the hydrate turned directly into α-NiMoO₄ above 483 K, giving nanorods thinner than the crystallites of the mother hydrate. On the other hand, it turned into Anderson type of polyoxomolybdate via a solid-solution process in a molybdate solution at room temperature.     

IM-16: A new microporous germanosilicate with a novel framework topology containing d4r and mtw composite building units

The synthesis and the structure of IM-16 a new germanosilicate with a novel zeolitic topology prepared hydrothermally with the ionic liquid 3-ethyl-1-methyl-3H-imidazol-1-ium as the organic structure-directing agent are reported. The structure of calcined and partially rehydrated IM-16 of chemical formula |(H₂O)_0.16|[Si_3.47Ge_2.53O₁₂] was solved from powder XRD data in space group Cmcm with a=15.0861(2) Å, b=17.7719(3) Å, c=19.9764(3) Å, V=5355.84(12) Å³ (Z=16). This new zeolite framework type contains 10-MRs channels and may be described from the d4r and mtw composite building units.     

Crystal structure of a new phosphate compound, Mg2KNa(PO4)2·14H2O

A new phosphate compound, Mg₂KNa(PO₄)₂·14H₂O, formed in the laboratory by cyanobacteria, has been identified and its crystal structure studied with single-crystal X-ray diffraction and infrared spectroscopy. The crystal is orthorhombic with the space group Pnma and unit-cell parameters a=25.1754(18) Å, b=6.9316(5) Å, c=11.2189(10) Å, V=1957.8(3) Å³. Its structure can be viewed as stacking of three types of layers along the a-axis in a sequence ABCBABCB…, where layer A is composed of Mg1(H₂O)₆ octahedra and Na(H₂O)₆ trigonal prisms, layer B of two crystallographically distinct PO₄³⁻ tetrahedra (designated as P1 and P2), and layer C of Mg2(H₂O)₆ octahedra and highly irregular K-polyhedra formed by five H₂O molecules and one O²⁻ from the P2 tetrahedron. The linkage between layers is principally achieved through hydrogen bonding, except for the K-O5 bond between layers B and C. The structure of Mg₂KNa(PO₄)₂·14H₂O has many features similar to those for the struvite analogs of MgK(PO₄)·6H₂O (Acta Crystallogr. B 35 (1979) 11) or MgNa(PO₄)·7H₂O (Acta Crystallogr. B 38 (1982) 40) and represents the first struvite-type phosphate compound that contains both K and Na as univalent cations.     

Structural researches on metal complexes with ligands containing the pyridoxal moiety: X-ray structure of chloro(N-pyridoxylidene-N′-salicyloylhydrazinato) copper(II) Monohydrate

Summary The x-ray crystal structure of the title complex is described Crystals are monoclinic, space groupP2₁/n, with unit-cell dimensions:a=18.070(2),b=13.471(2),c=6.788(2) Å,=94.70(1),Z=4. The structure was solved from diffractometer data by Patterson and Fourier methods and refined by least-squares techniques toR=5.0% for 2451 independent reflections. It consists of complex molecules, in which the copper atom square planar coordination comprises the chlorine atom, Cu-Cl=2.240(3) Å, and the organic ligand which acts as terdentate through the oxygen atom [Cu-O=1.948(3) Å] and a nitrogen atom, [Cu-N=1.933(5) Å] from the hydrazidic chain and the oxygen atom, [Cu-O = 1.894(4) Å] from the pyridoxal group.     

Synthesis and Structure of a Novel Layered Zincophosphate Zn4P3O11(OH)·3C3N2H4 with Organic Amine Acting as Ligand

A novel two-dimensional zinc phosphate Zn₄P₃O₁₁(OH)·3CN₂H₄ in which the structure-directing organic amine acts as a ligand has been synthesized hydrothermally. The structure was solved by single-crystal X-ray diffraction analysis. Crystal data: triclinic, space group P1? (No. 2) with lattice parameters a=9.5663(15) Å, b=9.8530(16) Å, c=12.3658(19) Å, α= 77.495(4)°, β=77.893(4)°, γ=68.175(3)°, V=1045.6(3) Å3, Z=2, R₁[I>2σ(I)]=0.0309, and wR₂[I>2σ(I)]=0.0809. Interestingly the structure involves a network of ZnO₄, PO₄, PO₃(OH), and the unusual ZnO₃N and ZnO₂N₂ tetrahedra with shared vertices. There are 10-membered rings in the layers, in which the structure-directing imidazole molecules reside. The other amine molecules protrude from the Zn centers and occupy spaces between the layers.     

Second sphere coordination in fluoroanion binding: Synthesis, spectroscopic and X-ray structural study of [Co(phen)2CO3](Pfbz)·6H2O

To explore the anion receptor potential of [Co(phen)₂(CO)₃]⁺ for the pentafluorobenzoate ion, [Co(phen)₂(CO)₃](Pfbz)·6H₂O (where phen = 1,10-phenanthroline and Pfbz = pentafluorobenzoate) was synthesized by reacting appropriate salts in aqueous medium. A detailed packing analysis has been undertaken to delineate the role of second sphere C-H?F interactions amid other heteroatom interactions. The complex salt has been characterized by elemental analyses, spectroscopic studies (IR, UV/Vis, multinuclear NMR) and solubility product measurement. The complex salt crystallizes in the monoclinic crystal system with space group P2₁/n having the cell dimensions a = 13.377(3) Å, b = 17.204(3) Å, c = 15.408(3) Å, β = 108.11(3)°, V = 3370.1(12) Å³ and Z = 4. Single crystal X-ray structure determination revealed ionic structure consisting of complex cation, [Co(phen)₂(CO)₃]⁺, Pfbz anion and six lattice water molecules. In the crystal lattice, discrete ions [Co(phen)₂CO₃]⁺ are forming rectangular voids in which the Pfbz anions are entrapped. Crystal lattice is stabilized by electrostatic forces of attraction and hydrogen bonding interactions, i.e. O-H?O, C-H?O, and C-H?F, involving second sphere coordination besides π?π interactions.     

A Vanadium (V) Hydroxymonophosphate Hydrate with a “Tape-Like” structure: K3(VO2)2PO4PO3OH·H2O

A new vanadium (V) hydroxymonophosphate hydrate, K₃(VO₂)₂PO₄PO₃OH·H₂O, with a “tape-like” structure has been synthesized. This compound crystallizes in the space group P2₁/c with a=5.099(1) Å, b=29.168(3) Å, c=8.115(1) Å, β=91.65(1)°. Its structure consists of [V₂P₂O₁₁OH]_∞ ribbons built up of corner-sharing VO₅ pyramids, PO₄, and PO₃OH tetrahedra, interleaved with K⁺ ions and H₂O molecules. In spite of its unidimensional character, this structure forms pentagonal tunnels. Relationships with frameworks involving tetragonal tunnels are studied.