Syntheses and crystal structures of four new fpa-metal complexes through in situ ligand reaction

Four new fpa-metal complexes, [Co(fpa)₂(H₂O)₂] (1), [Cu(fpa)₂(H₂O)] (2), [Zn₂(fpa)₄(bpp)₂] _n (3), and {[Zn(bpy)(H₂O)₄]?·?2(fpa)} _n (4), have been synthesized and fully characterized by elemental analyses, IR spectroscopy, single-crystal X-ray diffraction, and thermogravimetric analysis (TGA), (Hfpa?=?2,2-difluoro-2-(pyridine-2-yl)acetate, bpp?=?1,3-bis(4-pyridyl)propane, bpy?=?4,4′-bipyridine). X-ray diffraction analyses reveal that 1 and 2 with 0-D structures are both extended into 3-D supramolecular networks through hydrogen bonds and π···π interactions. Complex 3 with chiral centers possesses a 1-D structure constructed by two kinds of bpp molecules and four kinds of fpa^? molecules with different conformations, with bbp and fpa^? bridging and capped ligands, respectively. In 4, bpy links [Zn(H₂O)₄]²⁺ into a 1-D polymeric cationic chain and uncoordinated fpa^? compensates the framework charge. The results of TGA reveal that fpa^? decomposes through two processes. Both 3 and 4 show strong fluorescence in the solid state at room temperature.     

Self‐Assembly of 1,1′‐Biphenyl‐2,2′,6,6′‐tetracarboxylic Acid: Formation of an Achiral Grid with Chiral Compartments

D ₄ ‐symmetric chiral hydrogen‐bonded cyclotetramers (see the structure in the picture) are present in the self‐assembled achiral title compound in the solid state. The unilayered network set up from the chiral “square” blocks is achiral as a consequence of the crystal symmetry.     

氢转移聚合反应的研究

羟乙基丙烯酸酯(HEA)进行游离基型聚合,生成聚羟乙基丙烯酸酯(PHEA)的研究已有报道,但有关该化合物氢转移聚合反应仅有Saegusa等进行过研究,而在钠催化下的氢转移聚合反应却未见报道。本文研究了HEA在钠作用下的氢转移聚合反应,用IR、NMR、VPO和元素分析等手段研究了它的结构和分子量,讨论了反应机理。     

Syntheses,Crystal Structures and Properties of the Tetrametaphosphimates MII2(PO2NH)4 · 8 H2O with MII = Mg,Mn, Co and Zn

Mg₂(PO₂NH)₄ · 8 H₂O ( 1 ), Mn₂(PO₂NH)₄ · 8 H₂O ( 2 ), Co₂(PO₂NH)₄ · 8 H₂O ( 3 ) and Zn₂(PO₂NH)₄ · 8 H₂O ( 4 ) were obtained as microcrystalline powders by combining aqueous solutions of K₄(PO₂NH)₄ · 4 H₂O and MX₂ · y H₂O (M = Mg, Mn, Co, Zn; X = Cl, NO₃). Single crystals were obtained by crystallization in gelatine gels in U‐tubes or test‐tubes. 2 and 4 were characterized by thermogravimetry and 4 was additionally characterized by temperature dependend in situ powder diffractometry. The structures of 1 , 2 , 3 and 4 were found to be isotypic and were solved by single‐crystal X‐ray methods: P 2₁/c, Z = 2 ( 1 : a = 645.4(2), b = 1050.1(2), c = 1283.3(3) pm, β = 104.66(3)°; 2 : a = 648.7(2), b = 1063.1(2), c = 1310.8(3) pm, β = 103.93(3)°; 3 : a = 643.3(2), b = 1049.0(2), c = 1286.7(3) pm, β = 104.28(3)°; 4 : a = 644.18(5), b = 1049.22(7), c = 1282.43(8) pm, β = 104.122(6)°). The structure is composed of MO₆ octahedra and (PO₂NH)₄^4— anions. The P₄N₄ rings of the (PO₂NH)₄^4— anions exhibit a slightly distorted chair conformation, which is supported by IR data and has been described by torsion angles, Displacement Asymmetry Parameters and Puckering Parameters. Via M²⁺ ions and hydrogen bonds, the tetrametaphosphimate anions are connected forming layers perpendicular to [100]. These layers are connected by hydrogen bonds.     

Synthesis and Crystal Structure of the Hydrated Nickel(II) Complex of Tartrate

Abstract  A new dinuclear hydrated nickel(II) tartrate has been isolated and structurally characterized by single-crystal X-ray diffraction. The title compound formulated as [Ni₄(C₄H₄O₆)₄(H₂O)₈](EtOH)_0.5(H₂O)_10.25 (C₁₇H_55.5Ni₄O_42.75) crystallizes in monoclinic system, space group P2(1)/c with a = 13.684(5), b = 17.143(6), c = 18.586(6) ?, β = 96.638(6)°, V = 4331(3) ?³, Z = 4. The unit cell contains two crystallographic independent dimeric units of [Ni₂(C₄H₄O₆)₂(H₂O)₄] without significant structural difference, half of menthol molecule and ten and a quarter packing water molecules. In each dimeric unit, one (R,R)-tartrato dianion chelates two Ni(II) ions by the use of two hydroxy oxygen and two carboxyl oxygen atoms as donor atoms, and another tartrato dianion chelates the same pair of Ni(II) cations in the same way. Each Ni(II) atom is six-coordinated by six O atoms from two tartrate units and two water molecules. Index Abstract  The crystal structure of complex [Ni₄(C₄H₄O₆)₄(H₂O)₈](EtOH)_0.5(H₂O)_10.25 contains two crystallographic independent dimeric units of [Ni₂(C₄H₄O₆)₂(H₂O)₄] without significant structural difference. In each dimeric unit, one (R,R)-tartrato dianion chelates two Ni(II) ions by the use of two hydroxy oxygen and two carboxyl oxygen atoms as donor atoms, and another tartrato dianion chelates the same pair of Ni(II) cations in the same way.      

Effects of the bond dilution on the phase diagrams of a spin-1 transverse Ising model with crystal field interaction on a honeycomb lattice

A bond diluted spin-1 Ising model with crystal and transverse field interactions is examined for honeycomb lattice by introducing an effective field approximation that takes into account the correlations between different spins that emerge when expanding the identities. The effects of the crystal field as well as the transverse field and dilution on the phase diagrams and order parameter m_z are discussed in detail. A number of interesting and unusual phenomena such as reentrant phenomena and three successive phase transitions originating from the crystal field as well as the transverse field and bond dilution have been found.     

Kinetic Determination of Iodide Based on its Effect on the Hydrogen Peroxide Oxidation of Triflupromazine

Summary.  A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H₂O₂. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of H₂O₂. The optimum reaction conditions are TFP (0.4 × 10⁻³ M), H₂SO₄ (1.0M), H₃PO₄ (2.0M), and H₂O₂ (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm⁻³ and a detection limit of 0.04 ng ċ cm⁻³, based on the 3 S_b criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as 0.2, 1.0, 2.0, and 4.0 ng ċ cm⁻³ of I⁻, IO₃ ^-, or IO₄ ^- in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide determination. Received January 19, 2001. Accepted (revised) March 12, 2001     

Efficient Low-temperature Hydrogen Production by Electrochemical-assisted Methanol Steam Reforming

Methanol steam reforming (MSR) provides an alternative way for efficient production and safe transportation of hydrogen but requires harsh conditions and complicated purification processes. In this work, an efficient electrochemical-assisted MSR reaction for pure H₂ production at lower temperature (~140 °C) is developed by coupling the electrocatalysis reaction into the MSR in a polymer electrolyte membrane electrolysis reactor. By electrochemically assisted, the two critical steps including the methanol dehydrogenation and water-gas shift reaction are accelerated, which is attributed to decreasing the methanol dehydrogenation energy and promoting the dissociation of H₂O to OH* by the applied potential. Furthermore, the reduced H₂ partial pressure by the hydrogen oxidation and reduction process further promotes MSR. The combination of these advantages not only efficiently decreases the MSR temperature but also achieves the high rate of hydrogen production of 505 mmol H₂ g _Pt⁻¹ h⁻¹ with exceptionally high H₂ selectivity (99 %) at 180 °C and a low voltage (0.4 V), and the productivity is about 30-fold than that of traditional MSR. This study opens up a new avenue to design novel electrolysis cells for hydrogen production.     

First principles study of pressure induced structural phase transition in hydrogen storage material—MgH2

First principles calculation were performed using Vienna ab-initio simulation package within the frame work of density functional theory (DFT) to understand the electronic properties of magnesium hydride. At normal pressure, the most stable structure of MgH₂ is rutile type with a wide band gap of 3.52 eV, which agrees well with the available data. A pressure induced semi-conductor to metallic transition at a pressure of 92.54 GPa is predicted. Our results indicate a sequence of pressure induced structural phase transition in MgH₂. The obtained sequence of phase transition was α→γ→β→δ→ε at a pressure of 0.37 GPa, 3.89 GPa,7.23 GPa and 11.26 GPa, respectively. Thus our results indicate that MgH₂ is one of the best hydrogen storage material and the maximum storage capacity achieved was 7.7%.     

Facile Synthesis of Ultra‐wide Two Dimensional Bi2S3 Nanosheets: Characterizations,Properties and Applications in Hydrogen Peroxide Sensing and Hydrogen Storage

The ultra‐wide two dimensional Bi₂S₃ nanosheets (2D Bi₂S₃ Ns) as non‐toxic graphene‐like nanomaterials have been prepared through solvothermal decomposition of a single‐source precursor, Bi(S₂CNEt₂)₃, in ethylenediamine media for 2 h in 180 °C. The morphology, structure, properties and catalytic activity of prepared 2D Bi₂S₃ Ns were characterized with XRD, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV‐Visible spectroscopy, cyclic voltammetry (CV), amperometry, electrochemical charge/discharge technique and electrochemical impedance spectroscopy (EIS). The SEM image showed the 2D Bi₂S₃ Ns with a thickness of 15±4 nm and lengths of several micrometers is synthesized. The UV−Vis spectrum of 2D Bi₂S₃ Ns showed high sensitivity to visible‐near infrared light with its direct energy band gap of ≈1.22 eV. These Bi₂S₃ Ns showed high electron transfer ability and good electrochemical behavior and also exhibited electro‐catalytic activity toward the reduction‐oxidation of hydrogen peroxide. It is found that Bi₂S₃ Ns could detect H₂O₂ at wide linear concentration range (50.0 μM–8.0 mM) with detection limit 8 μM, using amperometry as measuring technique. Also the synthesized Bi₂S₃ Ns exhibited excellent electrochemical H₂ storage properties. As a result, based on above properties, the Bi₂S₃ Ns can be used as a valuable and useful nanomaterial for H₂ storage, high‐energy batteries, electrocatalytic fields and electrochemical sensing.