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C27H54N6O28V10, triclinic, P 1 ‾ $P‾{1}$ (no. 2), a = 11.3803(3) Å, b = 14.0832(4) Å, c = 16.2352(7) Å, α = 91.784(3) Å, β = 104.264(3) Å, γ = 107.112(2) Å, V = 2395.04(14) Å3, Z = 2, R gt (F) = 0.0291, wR ref (F 2) = 0.0810, T = 293(2) K.

C12H20Cl2N4Zn, monoclinic, P21/n (no. 14), a = 9.9915(9) Å, b = 13.0923(12) Å, c = 13.1894(13) Å, β = 98.794(2)°, V = 1705.0(3) Å3, Z = 4, Rgt (F) = 0.0453, wRref (F 2) = 0.1248, T = 298(2) K.

A series of Fe/h-BN catalysts promoted with Cu or Mn were prepared for Fischer-Tropsch synthesis (FTS). The physicochemical properties, crystal structures and morphologies of the catalysts were characterized by N2 physisorption, FT-IR, TPR, XPS, XRD, MES and TEM. It is found that iron oxide nanoparticles are highly dispersed on h-BN matrix due to the anchoring effect of surface defects and the accommodation of porous structures of h-BN. The characterization results indicate that strong interaction between iron oxide and h-BN is present on un-promoted catalyst, which endows the h-BN supported iron catalyst with stable properties under FTS conditions but severely retards reduction of the catalyst. The addition of Cu to Fe/h-BN can to some extent overcome the strong interaction by introducing more sites for dissociating H2. It is observed that Cu promoter can increase the reduction or carburization degree and thus enhance the FTS activity. The addition of Mn to Fe/h-BN can weaken the strong interaction by altering the electron structure of iron species. And the electron-rich Fe species are responsible for easy reduction and the enhanced FTS performance. Besides, a higher activity can be realized by co-adding Cu and Mn to the Fe/h-BN catalyst. These results suggest that the synergistic effect of Mn and Cu can largely improve the performance of Fe/h-BN catalyst without impairing the stability of the catalyst. The present study paves a way to tailor the performances of FTS catalysts with h-BN as support.

A novel 1-hydroxy-2,4-diformylnaphthalene-based fluorescent probe L was synthesized by a Knoevenagel reaction and exhibited excellent sensitivity and selectivity towards sulfite ions (SO32−) and bisulfite ions (HSO3−). The detection limits of the probe L were 0.24 μM using UV-Vis spectroscopy and 9.93 nM using fluorescence spectroscopy, respectively. Furthermore, the fluorescent probe L could be utilized for detection in real water samples with satisfactory recoveries in the range 99.20%~104.30% in lake water and 100.00%~104.80% in tap water by UV-Vis absorption spectrometry, and in the range 100.50%~108.60% in lake water and 102.70%~103.80% in tap water by fluorescence spectrophotometry.

Different content of Ti4+ has been successfully doped into the lattice sites of Cr3+ in NaCrO2 by the two step solid-state reaction. The analysis results of crystal structure demonstrate that the interslab (NaO2) spacing is increased with Ti doping content, which contributes to widening the sodium ion migration channel and then facilitating the rapid (de)intercalation capability of sodium ions. During charge-discharge processes, these O3-Na1-xCr1-xTixO2 (x = 0.03, 0.05, 0.1) layered oxides exhibit delayed O3-P3 phase transition and increased average discharge voltage due to stronger Ti-O bond relative to Cr-O bond. In particular, the Na0.95Cr0.95Ti0.05O2 shows the optimal electrochemical performance which releases a discharge specific capacity of 96.7 mAh g−1 at 1 C (100 mA g−1) with 80.1% capacity retention after 800 cycles. Even under the high rate of 30 C, it can deliver a discharge specific capacity of 67 mAh g−1.

(5Z, 7Z)-6, 8-dimethyl-9 H-tetrazolo [1,5-b] [1,2,4] triazepine (DMTT) is a fused ring nitrogen-rich compound, whose nitrogen content is 51.2%. In this study, the synthesis was carried out and the single crystal was cultivated for the first time. Gas generator based on DMTT with common oxidant was designed into formulation DMTT-KNO3. The combustion temperature, gas production rate, and mechanical safety of the gas generator were measured. In conclusion, DMTT/KNO3 formula has good combustion performance with low combustion temperature, fast gas production rate, and high safety in the process of movement and impact. The Inflation experiment of lifejacket airbag confirms that it is a kind of gas generator with potential development.

Class I terpene synthase (TPS) generates bioactive terpenoids with diverse backbones. Sesterterpene synthase (sester-TPS, C25), a branch of class I TPSs, was recently identified in Brassicaceae. However, the catalytic mechanisms of sester-TPSs are not fully understood. Here, we first identified three nonclustered functional sester-TPSs (AtTPS06, AtTPS22, and AtTPS29) in Arabidopsis thaliana. AtTPS06 utilizes a type-B cyclization mechanism, whereas most other sester-TPSs produce various sesterterpene backbones via a type-A cyclization mechanism. We then determined the crystal structure of the AtTPS18–FSPP complex to explore the cyclization mechanism of plant sester-TPSs. We used structural comparisons and site-directed mutagenesis to further elucidate the mechanism: (1) mainly due to the outward shift of helix G, plant sester-TPSs have a larger catalytic pocket than do mono-, sesqui-, and di-TPSs to accommodate GFPP; (2) type-A sester-TPSs have more aromatic residues (five or six) in their catalytic pocket than classic TPSs (two or three), which also determines whether the type-A or type-B cyclization mechanism is active; and (3) the other residues responsible for product fidelity are determined by interconversion of AtTPS18 and its close homologs. Altogether, this study improves our understanding of the catalytic mechanism of plant sester-TPS, which ultimately enables the rational engineering of sesterterpenoids for future applications., Sesterterpenoids, a relatively new group of terpenoids, are structurally diverse and widely distributed in bacteria, fungi, and the plant kingdom. However, the enzymatic mechanism of sesterterpene synthase (sester-TPS), the first committed biosynthesis step, remains obscure. This study reveals the critical amino acids controlling the substrate and product specificity of plant sester-TPS by determining the first crystal structure of the sester-TPS–FSPP complex.

The syntheses, crystal structures, IR and electronic absorption spectroscopy of cyanide-bridged complex trans -BrRu II (dppe) 2 ( μ -CN)(Fe III Br 3 ) ( 2 ) and its parent trans -ClRu II (dppe) 2 (CN) ( 1 ) were reported. The crystals crystallized in the monoclinic space group C 2/ c for 1 , and monoclinic space group P 2 1 / c for 2 . The crystal structural data, MMCT (metal-to-metal charge transfer) in electronic absorption spectra and EPR spectra indicate the existence of some electron delocalization along Fe III NC Ru II in complex 2 . The magnetic properties of complex 2 were measured and analyzed.

The star-shaped lattice structure is recognized as a typical auxetic metamaterial. Unlike the most research focused on the negative Poisson's ratio, in this paper the wave propagation behaviour and vibration attenuation mechanism of the periodic star-shaped lattice structure are studied based on the analytical 16 degrees of freedom (DOF) discrete mass-spring model. The dispersion relation and bandgaps of the 16 DOF mass-spring model are derived based on lattice dynamics. The dependence of the bandgap boundaries on the parameters of configuration angle, stiffness, and mass are studied accordingly. It is noteworthy that the eigenstate modes investigation reveals that the bandgaps attribute to the hybridization of the monopole, dipole, quadrupole, and rotational resonance, which is only noticed in multiphase hybrid metamaterials before. Most importantly, though examining the eigenstate modes of the degeneration points, the low-frequency bandgap between the acoustic and optical dispersion curves is opened by tuning the dominant parameters. The response of the finite periodic star-shaped lattice shows the frequency ranges with high attenuation agree well with complete bandgaps predicted by dispersion relation. The star-shaped lattice shows a very unique anisotropic solid when the slope of the dispersion curve is negative.

C7H10N4O, monoclinic, I2 (no. 5), a = 15.7815(13) Å, b = 4.3242(3) Å, c = 12.4658(9) Å, β = 106.301(8)°, V = 816.50(10) Å3, Z = 4, R gt(F) = 0.0473, wR ref(F 2) = 0.1067, T = 113.25(10) K.

We have investigated the chirality transfer from 1-phenylethylamine to a 5-amino-1,3-phthalic acid diamide-linked zinc bisporphyrinate through crystallographic and DFT studies. When the hosts were mixed with optically pure 1-phenylethylamine, CD showed moderate signals in the Soret band region. Single crystals of the corresponding 1:1 and 1:2 host-guest complexes were obtained. We present the first crystallographic structure of a 1:2 host-guest complex consisting of a bisporphyrin host and chiral monoamine guests. The structure reveals that the host-guest interactions are different for two guest molecules. The first guest is involved in a hydrogen bond and π-π interactions, while the second one is only involved in π-π interactions, which has not been observed in previous studies. The corresponding chirality transfer mechanism was also rationalized by DFT calculations.

International audience; Properdin (FP) is a positive regulator of the immune system stimulating the activity of the proteolytically active C3 convertase C3bBb in the alternative pathway of the complement system. Here we present two crystal structures of FP and two structures of convertase bound FP. A structural core formed by three thrombospondin repeats (TSRs) and a TB domain harbors the convertase binding site in FP that mainly interacts with C3b. Stabilization of the interaction between the C3b C-terminus and the MIDAS bound Mg2+ in the Bb protease by FP TSR5 is proposed to underlie FP convertase stabilization. Intermolecular contacts between FP and the convertase subunits suggested by the structure were confirmed by binding experiments. FP is shown to inhibit C3b degradation by FI due to a direct competition for a common binding site on C3b. FP oligomers are held together by two sets of intermolecular contacts, where the first is formed by the TB domain from one FP molecule and TSR4 from another. The second and largest interface is formed by TSR1 and TSR6 from the same two FP molecules. Flexibility at four hinges between thrombospondin repeats is suggested to enable the oligomeric, polydisperse, and extended architecture of FP. Our structures rationalize the effects of mutations associated with FP deficiencies and provide a structural basis for the analysis of FP function in convertases and its possible role in pattern recognition.

Uniform SSZ-39 (Si/Al ratio ∼12) crystals with an average size of about one micron were synthesized and used to support Pd (0.7–3 wt%) for PNA. The as-synthesized materials were characterized by FTIR, XRD, Helium Ion Microscopy, HAADF-STEM imaging, 27Al, 29Si, and 1H-29Si CP solid state NMR spectroscopic techniques. FTIR studies with CO and NO probe molecules reveal that the majority of Pd is dispersed as isolated Pd(II) and Pd(II)−OH centers and as such is suitable as a low-temperature passive NOx adsorber. Pd(II)-NO, Pd(II)(OH)(NO), and Pd(II)(CO)(NO) complexes form in this material during PNA. Comparison to Pd/SSZ-13 (Si/Al ∼12) shows the superior hydrothermal stability of this new material, surviving hydrothermal aging up to 815 °C in 10 % H2O/Air for 16 h without a significant loss of activity. The SSZ-39 crystal structure remains intact during hydrothermal aging up to 1000 °C confirmed by XRD and HAADF-STEM imaging/EDS mapping. However, changes to the framework, as evidenced by high-field 27Al NMR, during such severe hydrothermal treatment significantly alter the NOx release profiles. Besides PNA, this hydrothermally stable material (3 wt% Pd on SSZ-39; Si/Al ∼12) can be used as a robust methane combustion catalyst under practically relevant conditions (i.e., GHSV∼300 L/g*hr). This catalyst shows minimal deactivation after both hydrothermal aging at 750 and 800 °C and prolonged time on stream (105 h) at 425°C. In contrast, both 3 wt% Pd/alumina and 3 wt% Pd/SSZ-13 lose a significant portion of their activity under such conditions, marking an improvement over current technology.

Recent experimentally observed intrinsic ferromagnetism in two-dimensional (2D) van der Waals crystals has ignited substantial interests due to their great potential in spintronic devices. However, their practical applications are hampered by rather low Curie temperature and small magnetic anisotropic energy. Here, we predict from first-principles calculations that the 2D pristine hexagonal manganese carbide (h-MnC) sheet exhibits robust ferromagnetic and half-metallic features with complete spin polarization, sizable magnetic anisotropic energy, and wide half-metallic gap near the Fermi energy level. Moreover, the h-MnC sheet can retain its structure up to the temperature of 1000 K, indicating a highly thermodynamic stability. The Monte Carlo simulations based on the Heisenberg model with single-ion anisotropy predict a Curie temperature of 233 K in 2D h-MnC crystal. We confirm the robustness of the ferromagnetism and half-metallicity against the external strain from −6% to 10%. Also, a feasible experimental fabrication route is proposed to realize the h-MnC monolayer via heterostructure engineering and exfoliation techniques. Overall, the robustness of the half-metallicity in combination with the high-temperature ferromagnetism render the freestanding h-MnC monolayer and even its energetically favorable h-MnC/MoS2 and h-MnC/MoSe2 heterostructures quite promising materials for developing practical spintronic nanodevices.

Polyglyceryl fatty acid ester (PGE) was used as organogelator to structure sunflower oil. Macroscopic properties, microstructures, interaction force of organogels were systematic analysed using rheometer, pulsed nuclear magnetic resonance (pNMR), differential scanning calorimetry (DSC), polarizing light microscope (PLM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR), respectively. In addition, organogels were evaluated as a shortening replacer applied in bread. Macroscopic properties were related to the space-spanning networks formed through surface interactions among crystalline such as hydrogen bonds and electrostatic interaction. Higher organogelators concentration resulted in more compact network which provided lower oil loss, higher firmness and G'. Melting and collapsing of crystalline structure resulted in the transformation of organogel from solid-like state to liquid state. In bread making process, the crystalline network formed by PGE could imitated the functions of crystalline network structures formed by triacylglycerol. This investigation was beneficial for expanding potential applications of PGE in organgels.

C24H29N5O, triclinic, P1̄ (no. 2), a = 10.352(9) Å, b = 10.911(10) Å, c = 12.480(6) Å, α = 97.33(2)°, β = 110.29(2)°, γ = 115.353(15)°, V = 1129.6(15) Å3, Z = 2, R gt(F) = 0.0614, wR ref(F 2) = 0.1855, T = 296(2) K.

The effects of Pt precursors on the performance of Pt/ZSM-22 catalysts for n -hexadecane hydroisomerization were investigated with 0.5 wt.% platinum loading using three platinum precursors: Pt(NO 3 ) 2 , H 2 PtCl 6 , and Pt(NH 3 ) 4 Cl 2 . The catalyst derived from H 2 PtCl 6 exhibits the highest platinum dispersion and n Pt/ n A value and displays better isomerization activity and selectivity. Three effects can be traced back to the precursors: the valence state of Pt, the location of Pt (in cationic or anionic group), and the existence of chloride. The predominant effect is that of valence states of Pt in precursors, which play a crucial role in determining the textural properties (both particle size and crystal structure) of catalysts. Different crystal orientations of Pt 0 are found on the reduced samples, with Pt(IV) precursors oriented along the [0 1 1] crystallographic axis, while those with Pt(II) precursors are oriented along the [0 0 1] axis. The former favors smaller Pt particles and exposes more active Pt{1 1 1} corner sites, while the latter exhibits larger Pt particles and exposes more Pt{1 0 0} facets, as revealed by combining HRTEM with CO-IR studies. Moreover, Pt{1 1 1}/ZSM-22 shows higher isomerization selectivity than Pt{1 0 0}/ZSM-22. The other effect is location of Pt in precursors. Compared with the sample using Pt(NH 3 ) 4 Cl 2 precursor, the catalyst with (NH 4 ) 2 PtCl 4 precursor exhibits smaller particles and higher platinum dispersion and facilitates isomerization reactivity. The existence of chloride is also a nonignorable effect. The samples containing chloride ions without amine groups in precursors favor platinum dispersion due to avoiding autoreduction by NH 3 during the calcination process.

The syntheses, crystal structures, IR and electronic absorption spectroscopy of two cyanide precursors cis-MII(dppm)2(CN)2 (M = Ru, 1; Os, 2) (dppm = bis(diphenylphosphino)methane) and four new cyanide-bridged complexes cis-MII(dppm)2(CN)2(FeIIIX3)2 (M = Ru, X = Cl, 3; M = Ru, X = Br, 4; M = Os, X = Cl, 5; M = Os, X = Br, 6) are reported. The crystal structural data, IR and the MMCT (metal-to-metal charge transfer) in the electronic absorption spectroscopy indicate the existence of some electron delocalization along FeIII–NC–MII arrays in complexes 3–6. The presence of a newer MMCT band of the Os-based complexes (5 and 6) than the Ru-based complexes (3 and 4) should result from the larger spin–orbit coupling (SOC) of OsII. Also the theoretical calculated values of the crystal structural data and IR spectra are consistent with the experimental values. Temperature-dependent magnetic properties of complexes 3–6 reveal the presence of the very weak metal–metal interaction between distant FeIII ions.

A nitrogen doped BiOCl (N-BiOCl) photocatalyst was synthesized and characterized using an ethylenediamine-assisted hydrothermal method. The N-BiOCl sample demonstrated the same tetragonal crystal structure as the as-prepared pure BiOCl sample. SEM results indicated that N-BiOCl sample was self-assembled by nanoplates to provide an aggregated flower-like microstructure. Doped nitrogen was substituted for oxygen in the crystal lattice of BiOCl, causing a red shift for N-BiOCl sample compared to BiOCl sample. The N-BiOCl sample exhibited higher photocatalytic activity in the degradation of Rhodamine B under visible light than observed in BiOCl sample, and the stability of the sample was verified. Meanwhile, speculative causes for the enhancement in the photocatalytic activity of N-BiOCl sample were also proposed.

Based on the selectivity of deprotonation of 5,5'-bistrimethylsilyl-2,3'-bithiophene (4) in the presence of n-BuLi, three new cyclooctatetrathiophenes (COThs), COTh-1, COTh-2, and COTh-3 have been efficiently developed via intermolecular or intramolecular cyclizations. Their crystal structures clearly show that the different connectivity sequence of the thiophene rings in the molecules. The CV data and UV-vis absorbance spectra of COThs are also described. In addition, the time-dependent density functional theory (TDDFT) calculations accurately reproduce experimental observations and afford band assignment.

As a part of a serial work about the annealing inducing improvement of fracture toughness of polypropylene (PP) articles, in this work, a highly efficient mobilizer was introduced into PP and the injection-molded samples were annealed at different temperatures. The mobility of chain segments of PP was investigated by measuring the glass transition temperature. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) were used to characterize the variation of crystalline structure of PP during the annealing process. The fracture behaviors including notched Izod impact fracture and universal tensile fracture were investigated to detect the mechanical properties in response to the variations of both chain segments mobility and crystalline structures. It was found that the mobilizer greatly improved the chain segments mobility. Further results showed that the mobilizer also induced apparent changes of the glass transition temperature and the degree of crystallinity of PP during the annealing process. Consequently, the annealed PP samples containing a few amount of mobilizer exhibited largely increased fracture toughness.

Fossil blister pearls attached to the shells of an Anodonta mollusk from China, early Early Pleistocene, are reported here for the first time. The pearls were investigated in detail using a variety of methods. Micro-CT scanning of the fossil pearls was carried out to discover the inner structure and the pearl nucleus. Using CTAn software, changes in the gray levels of the biggest pearl, which reflect the changing density of the material, were investigated. The results provide us with some clues on how these pearls were formed. Sand grains, shell debris or material with a similar density could have stimulated the development of these pearls. X-ray diffraction analysis of one fossil pearl and the shell to which it was attached reveals that only aragonite exists in both samples. The internal structures of our fossil shells and pearls were investigated using a Scanning Electron Microscope. These investigations throw some light on pearl development in the past.

Reaction of 2-C5H4 NCOSPh, generated from 2-C5H4NCO2H and PhSH in the presence of DCC, with Fe3(CO)12 affords (μ-κ2C,N-2-C5H4N)(μ-PhS)Fe2(CO)6 (1) and (μ-PhS)2Fe2(CO)6 (2). Reaction of (NC)2C=C(SMe)2, formed from NCCH2CN, CS2, and MeI in the presence of NaOH, with Fe3(CO)12 provides (μ-κ2C,S-(NC)2C=CSMe)(μ-MeS)Fe2(CO)6 (3) and (μ-MeS)2Fe2(CO)6 (4). All complexes have been fully characterized by EA, IR, 1H NMR, and 13C NMR spectroscopy and structurally determined by X-ray crystallography. In 1 and 3, the group attached to the bridging S is at the equatorial position. In 2, two phenyl groups are at equatorial positions. Two isomers of 4, ae-4 and ee-4, can be separated by thin-layer chromatography. DFT calculations reveal that the Gibbs energy difference between ae-4 and ee-4 is −2.17 kcal mol−1 in THF and −2.29 kcal mol−1 in benzene, and the isomerization barrier between ae-4 and ee-4 is 14.92 kcal mol−1 in THF and 16.84 kcal mol−1 in benzene. All these results suggest that ae-4 is more stable than ee-4 in either THF or benzene, and the two isomers do not interconvert. Electrochemical studies of 1 and 3 demonstrate that using HOAc as a proton source 1 and 3 can catalyze H2 production.

The correlation of carbonate content with enamel microstructure (chemical and crystal structure) and mechanical properties was evaluated via linear mapping analyses using Raman microspectroscopy and nanoindentation. Mappings started at the outer enamel surface and ended in the inner enamel near the dentin-enamel junction (DEJ) in lingual and buccal cervical and cuspal regions. The carbonate peak intensity at 1070 cm−1 gradually increased from outer to inner enamel. Moreover, the phosphate peak width, as measured by the full width at half maximum (FWHM) of the peak at 960 cm−1, also increased, going from ~9 cm−1 in outer enamel to ~13 cm−1 in enamel adjacent to the DEJ, indicating a decrease in the degree of crystallinity of hydroxyapatite from outer to inner enamel. In contrast, Young’s modulus decreased from 119±12 to 80±19 GPa across outer to inner enamel with a concomitant decrease in enamel hardness from 5.9±1.4 to 3.5±1.3 GPa. There were also significant correlations between carbonate content and associated crystallinity with mechanical properties. As carbonate content increased, there was an associated decrease in crystallinity and both of these changes correlated with decreased modulus and hardness. Collectively, these results suggest that enamel carbonate content and the associated change in the crystal structure of hydroxyapatite, i.e. degree of crystallinity, may have a direct effect on enamel mechanical properties. The combination of Raman microspectroscopy and nanoindentation proved to be an effective approach for evaluating the microstructure of enamel and its associated properties.

A family of paramagnetic cyanido-bridged 1-D heteronuclear zigzag chain isostructural complexes, [cis-M(bpy)2(CN)2Mn(salen)](PF6) (M = Fe, 1; M = Ru, 2; M = Os, 3; bpy = 2,2′-bipyridine, salen = N,N′-ethylenebis(salicylideneaminato)dianion) and [cis-Os(bpy)2(CN)2Mn(salcy)](PF6) (4) (salcy = N,N′-(1,2-cyclohexanediylethylene) bis(salicylideneiminato)dianion), were synthesized by the reaction of diamagnetic precursors cis-M(bpy)2(CN)2 (M = Fe, Ru, Os) with paramagnetic Mn(III) Schiff bases, respectively. All these complexes were fully characterized by IR, MS, elemental analysis, and single-crystal X-ray diffraction. Electronic absorption spectral and electrochemical properties of 1–4 have also been measured. The temperature dependence of magnetic susceptibilities suggests that magnetic interactions in 1–4 are very weak and can be considered to have disappeared.

In the title compound, C10H10N2O6·H2O, the carboxylic acid group and the nitro group are essentially coplanar with the benzene ring [maximum deviation = 0.0264 (9) Å], while the amide group is oriented at a dihedral angle of 9.22 (5)° with respect to the benzene ring. In the crystal, classical O—H...O and N—H...O hydrogen bonds and weak C—H...O interactions link the organic molecules and water molecules of crystallization into a three-dimensional supramolecular architecture.

A novel open-framework oxovanadium arsenate has been hydrothermally synthesized. It crystallizes in space group I(4) over bar 3m with cell parameters of a = 16.708(2) Angstrom, V = 4664.4(9) Angstrom(3) and Z = 4. Its structure is composed of a new type of decavandium cluster, which is constructed by two pentamers. Linking this decavanadate by AsO4 tetrahedral, a three-dimensional open-framework structure forms, which possesses large cavities. These high symmetric cavities interconnected through 12-membered ring windows forming a three-dimensional channel system. Catalytic measurements indicate that this compound is active for phenol hydroxylation using hydrogen peroxide as the oxidant. Catechol, hydroquinone and benzoquinone are the main products with 15.8% conversion of phenol (taking no account of the secondary product of tar) and 59.6% selectivity for hydroquinone, when the reaction was performed in water at 60degreesC for 6 h. (C) 2002 Elsevier Science (USA). All rights reserved.

The novel title Zn(II) coordination polymer, poly[bis(mu-6-thioxo-1,6-dihydropyridine-3-carboxylato-kappa(2)S:O)zinc(II)], [Zn(C6H4NO2S)2]n, consists of two crystallographically independent zinc centers and two 6-mercaptonicotinate (Hmna-) ligands. Each Zn(II) atom is four-coordinated and lies at the center of a distorted tetrahedral ZnS2O2 coordination polyhedron, bridged by four Hmna- ligands to form a two-dimensional (4,4)-network. Each Hmna- ion acts as a bridging bidentate ligand, coordinating to two Zn(II) atoms through the S atom and a carboxyl O atom. The metal centers reside on twofold rotation axes. The coordination mode of the S atoms and N-H...O hydrogen-bonding interactions between the protonated N atoms and the uncoordinated carboxyl O atoms give the extended structure a wavelike form.

In the title molecule, C26H20N2S2, the two benzene rings connected by a disulfide chain form a dihedral angle of 84.9 (1)°, and the two benzene rings in the two benzylideneaminophenyl fragments form dihedral angles of 34.4 (1) and 32.8 (1)°. The crystal structure exhibits weak intermolecular C—H...S hydrogen bonds, which link the molecules into chains along [101].

In the crystal structure of the title compound, C4H10NO2+·Cl− (systematic name: 3-ethoxy-3-oxopropan-1-aminium chloride), there are strong intermolecular N—H...Cl, C—H...Cl and C—H...O hydrogen-bonding interactions between the free chloride anion and the organic cation, resulting in a two-dimensional supramolecular network in the ab plane.

In the title mol-ecule, C(18)H(21)ClN(2)O(3)S, the pyrimidine ring exhibits a half-chair conformation. The ethyl group is disordered between two positions in a ratio 0.74:0.26. In the crystal structure, the mol-ecules are linked into chains along the a axis by N-H⋯O hydrogen bonds.

The asymmetric unit of the title compound, [Cd(C(7)H(7)N(2)O(4))(2)(H(2)O)(2)]·2H(2)O, consists of one Cd(II) ion, one 4-carb-oxy-2-ethyl-1H-imidazole-5-carboxyl-ate anion, one coordinated water mol-ecule and one lattice water mol-ecule. The Cd(II) ion lies on a twofold axis, and is hexa-coordinated by four O atoms from water mol-ecules and carboxyl-ate groups and two N atoms from two imidazole rings, in a distorted octa-hedral arrangement. An extensive framework of N-H⋯O and O-H⋯O hydrogen bonds with the participation of coordinated and free water mol-ecules is found in the crystal structure, which contributes to the formation of a three-dimensional structure.

In the title mol-ecule, C(16)H(17)N(3)O, the two aromatic rings form a dihedral angle of 4.51 (18)°. In the crystal structure, inter-molecular N-H⋯O hydrogen bonds link mol-ecules related by translation along the a axis into ribbons.

The title compound, C15H13NO2, was synthesized by N-alkylation of methyl bromoacetate with 9H-carbazole. The carbazole ring system is essentially planar (mean atomic deviation = 0.0346 Å) and makes a dihedral angle of 86.5 (7)° with the methyl acetate group. Weak intermolecular C—H...O hydrogen bonding is present in the crystal structure.

In the title compound, C22H19NO, the dihedral angle between the benzene ring and the carbazole ring system 77.1 (1)°.. The crystal structure is stabilized by intermolecular aromatic π–π interactions between the benzene ring and the pyrrole ring of the carbazole system of neighbouring molecules [centroid–centroid distance = 3.617 (4) Å]. In addition, the crystal structure exhibits a weak intermolecular C—H...π interaction.

In the title molecule, C21H16Cl2O2S, the five-membered ring is rotationally disordered between two orientations in a 1:1 ratio. In the crystal structure, weak intermolecular C—H...O hydrogen bonds link molecules related by translation along the a axis into chains, which are further combined into layers parallel to the bc plane via C—H...π interactions. The crystal studied was a racemic twin with a 0.37 (19):0.63 (19) domain ratio.

The asymmetric unit of the title compound, C19H16O2S2, contains two independent molecules with slightly different conformations. In the crystal structure, weak intermolecular C—H...O hydrogen bonds [C...O = 3.279 (15) and 3.407 (16) Å] link the molecules into chains extended along the c axis.

The hydrated title compound, C8H12O7·H2O, was isolated from the Chinese yam Dioscorea opposita Thunb. An intra­molecular O—H⋯O hydrogen bond occurs in the organic mol­ecule. In the crystal structure, the mol­ecules are linked by inter­molecular O—H⋯O hydrogen bonds, thereby forming chains propagating in [010].

The title compound (systematic name: methyl 3-carboxy-2-carboxymethyl-2-hydroxypropanoate), C7H10O7, was isolated from the Chinese yam Dioscorea opposita Thunb. In the crystal structure, the molecules present a two-dimensional structure arising from intermolecular O—H...O hydrogen bonds.

The title mol­ecule, C8H16N2O2, possesses a crystallographically imposed center of symmetry. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds link the mol­ecules into ribbons extended along the a axis.