Structure and Luminescent Property of a Novel 4-Hydroxyquinoline-2-carboxylate Based Zn（Ⅱ） Complex

A 3D coordination polymer [Zn2(hqc)2(H2O)]n has been obtained from the reaction of 4-hydroxyquinoline-2-carboxylic acid (H2hqc) with zinc(II) salt under hydrothermal condition, and characterized by elemental analysis, IR, TGA, PXRD and X-ray single-crystal diffraction. The complex crystallizes in the monoclinic system, space group P21/c with a = 14.305(2), b = 9.132(2), c = 15.356(2), β = 103.586(7)o, V = 1949.9(4)3, Z = 4, Dc = 1.782 g/cm3, μ = 2.508 mm-1, Mr = 523.06, F(000) = 1048, T = 293(2) K, λ(MoKα) = 0.71073, S = 1.008, the final R = 0.0329 and wR = 0.0745 for 3849 observed reflections (I > 2σ(I)). The title complex features a 3D framework via Zn(2) linking the 1D {Zn1(hqc)2}n chains. Thermogravimetric analysis shows that its framework is highly thermally stable up to 556 ℃ in the solid state.     

氧化铅在氨基甲酸乙酯与乙醇合成碳酸二乙酯反应中的催化作用

研究了氧化铅在氨基甲酸乙酯(EC)与乙醇反应合成碳酸二乙酯(DEC)中的催化作用.结果表明,氧化铅具有很好的稳定性,重复使用5次,其催化活性无明显下降.回收的催化剂为立方晶相金属Pb和斜方晶相PbO2的混合物,结合反应结果可认为,该混合物为反应的活性组分.结果还发现,PbO与DEC反应是PbO被还原为Pb的主要原因.     

Enantioselective α-hydroxylation of β-keto esters catalyzed by chiral S-timolol derivatives

A screen of aryloxy aminopropanol organocatalysts derived from the β-blocker inhibitor S-timolol determined the most active catalyst of asymmetric α-hydroxylation of β-keto esters. (R)-1-(tert-butylamino)-3-(3,4,5-trimethoxyphenoxy) propan-2-ol (3k) was the most effective derivative, enantioselectively catalyzing α-hydroxylation of β-keto esters using tert-butyl hydroperoxide as the oxidant in hexane to afford the corresponding products in excellent yield and with good enantioselectivity (up to 96% yield, 88% ee).     

Two New Cerebrosides from the Aerial Parts of Tithonia diversifolia

Two new cerebrosides, (2R)‐N‐{(1S,2S,3R,8E)‐1‐[(β‐D ‐glucopyranosyloxy)methyl]‐2,3‐dihydroxyheptadec‐8‐en‐1‐yl}‐2‐hydroxyhexadecanamide ( 1 ) and (2R)‐N‐{(1S,2R,8E)‐1‐[(β‐D ‐glucopyranosyloxy)methyl]‐2‐hydroxyheptadec‐8‐en‐1‐yl}‐2‐hydroxyhexadecanamide ( 2 ), were isolated from the aerial parts of Tithonia diversifolia (Hemsl .) A. Gray. Their structures were determined on the basis of spectroscopic analysis (IR, HR‐ESI‐MS, and 1D‐, and 2D‐NMR).     

Three novel organic-inorganic complexes based on decavanadate [V10O28]6- units: special water layers, open 3D frameworks and yellow/blue luminescences

Three unusual polyoxovanadate-based inorganic-organic hybrid complexes, [Zn(Im)(2)(DMF)(2)](2)[H(2)V(10)O(28)]·Im·DMF (1), [Zn(3)(Htrz)(6)(H(2)O)(6)][V(10)O(28)]·10H(2)O·Htrz (2) and {[Zn(3)(trz)(3)(H(2)O)(4)(DMF)](2)[V(10)O(28)]·4H(2)O}(n) (3) (Im = imidazole, Htrz = 1,2,4-triazole, DMF = N,N'-dimethylammonium) have been synthesized at room temperature via evaporative crystallization, and characterized by single-crystal X-ray diffraction. Complex 1 shows the structure of a discrete [V(10)O(28)](6-) cluster grafted by two [Zn(Im)(2)(DMF)(2)](2+) fragments through two bridged oxygen atoms, representing a rarely observed coordination mode. Complex 2 consists of a linear trinuclear Zn(II) unit bridging six Htrz ligands and a [V(10)O(28)](6-) cluster as the counter anion, where the extensive hydrogen-bonding interactions lead to {Zn(3)-V(10)}(SMF) and a special water layer involving (H(2)O)(36) rings, and consequently forms a unique 3D metal-organic-water supramolecular network. Complex 3 can be described as a 3,4-connected fsc-type network, and is the first example of open coordination 3D framework based on [V(10)O(28)](6-) and the other two different secondary building units, involving mononuclear and binuclear Zn(II)-Htrz motifs. The optical properties of complexes 1-3 in the solid state are investigated at room temperature. The results show that complexes 1 and 3 emit intense blue luminescences attributed to the ligands, while complex 2 exhibits an infrequent fluorescent property, emitting both blue and yellow luminescences at 472 and 603 nm simultaneously. Furthermore, powder X-ray diffraction and thermogravimetric analyses of 1-3 are also investigated, which demonstrate their high purities and thermal stabilities.     

The first principle studies of the structural and vibrational properties of solid β-HMX under compression

The structural, vibrational and electronic properties of β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (β-HMX) crystal under high pressure up to 40 GPa have been studied using density functional theory (DFT). The pressure dependences on the cell volume, lattice constants, and molecular geometry of solid β-HMX are presented and discussed. It is found that the N–N bonds are significantly reduced under compression, which may be of importance for initial decomposition. Based on the optimized crystal structures, the vibrational frequencies for the internal and lattice modes of the β-HMX crystal at ambient and high pressures are computed, and the pressure-induced frequency shifts of these modes are discussed.     

Structure and Shape Memory Properties of Polyurethane Copolymers Having Urethane Chains as Soft Segments

Shape memory polyurethanes are usually fabricated with low-molecular weight polyols through a two-step copolymerization, which often results in difficulty attaining both desired shape memory switch temperature and optimal thermomechanical properties. Here we present a series of shape memory polyurethane copolymers having urethane chains as soft segments. The structure and shape memory properties of copolymers were investigated with differential scanning calorimetry, dynamic mechanical analysis, small angle x-ray scattering, and thermomechanical tests. Increasing the length of the urethane soft segments enhanced phase separation, while it brought little change to the glass transition temperature (T _g). Based on the urethane soft segments, some rigid chain extenders could be readily introduced into the backbone of copolymers, resulting in better phase separation. All polyurethane copolymers exhibited more than 90% of shape recovery. The shape recovery of the materials was proved to be inversely proportional to the fraction of hard phase and directly proportional to the stability of hard domains. The copolymers containing longer soft and hard segments and rigid chain extenders exhibited higher deformation stress and thus larger recovery stress. The copolymerization employing urethane chains as soft segments can greatly expand flexibility for molecular design and favor the optimization of shape memory properties.     

Experimental Study on Flow Boiling Pressure Drop and Flow Instabilities of Reentrant Micro-channels

Flow boiling pressure drop and flow instabilities of Ω-shaped reentrant copper micro-channels were experimentally explored. Tests were conducted in deionized water and ethanol at inlet subcoolings of 10°C and 40°C, mass fluxes of 125–300 kg/m²·s, and a wide range of heat fluxes and exit vapor qualities. The operational parameters effects, i.e., heat flux, mass flux, inlet subcooling, and coolants, on pressure drop and flow instabilities were systematically explored. The two-phase pressure drop of reentrant micro-channels were found to generally increase monotonically with increasing heat fluxes and exit vapor qualities. Nevertheless, the roles of mass flux and inlet subcooling were dependent on the test coolant.     

Imaging interfacial micro‐ and nano‐bubbles by scanning transmission soft X‐ray microscopy

Synchrotron‐based scanning transmission soft X‐ray microscopy (STXM) with nanometer resolution was used to investigate the existence and behavior of interfacial gas nanobubbles confined between two silicon nitride windows. The observed nanobubbles of SF₆ and Ne with diameters smaller than 2.5 µm were quite stable. However, larger bubbles became unstable and grew during the soft X‐ray imaging, indicating that stable nanobubbles may have a length scale, which is consistent with a previous report using atomic force microscopy [Zhang et al. (2010), Soft Matter, 6 , 4515–4519]. Here, it is shown that STXM is a promising technique for studying the aggregation of gases near the solid/water interfaces at the nanometer scale.     

Orthogonality and quintic functional equations

Using the fixed point method, we prove the Hyers Ulam stability of an orthogonally quintic functional equation in Banach spaces and in non-Archimedean Banach spaces.