Mononuclear eight-coordinate (NH4)3[YIII(Nta)2] and one-dimensional unlimited zigzag type nine-coordinate {K[YIII(Egta) · 4H2O}n complexes: Syntheses and structural determination

The title complexes (NH₄)₃[Y^III(Nta)₂] (I) (H₃Nta = nitrilotriacetic acid) and {K[Y^III(Egta)] · 4H₂O} _n (II) (H₄Egta = ethyleneglycol-bis-(2-aminoethylether)-N,N,N′,N′-tetraacetic acid) were prepared, and their molecular and crystal structures were determined by single-crystal X-ray diffraction techniques. Complex I crystallizes in the rhombohedral crystal system with R $ \bar 3 $ \bar 3 c space group. The central Y³⁺ ion is eight-coordinated by two nitrogen and six oxygen atoms, which come from two tetradentate Nta ligands. The crystal data are as follows: a = 7.9340(14) ?, c = 54.611(15) ?, V = 2977.1(11) ?³, Z = 6, ρ_calcd = 1.738 mg/cm³, μ = 3.011 mm⁻¹, F(000) = 1596, R = 0.0234 and wR = 0.0641 for 686 observed reflections with I ≥ 2σ(I). The {K[Y^III(Egta)] · 4H₂O} _n is nine-coordinated by two nitrogen and seven oxygen atoms and produces a 1D unlimited zigzag-type chain through a bridging carboxylic group. {K[Y^III(Egta)] · 4H₂O} _n crystallizes in the monoclinic crystal system with C2/c space group. The crystal data are as follows: a = 37.588(5) ?, b = 13.7101(19) ?, c = 8.6070(12) ?, β = 99.929(2)°, V = 4369.0(11) ?³, Z = 8, ρ_calcd = 1.753 mg/cm³, μ = 2.934 mm⁻¹, F(000) = 2368, R = 0.0385 and wR = 0.0800 for 4082 observed reflections with I ≥ 2σ(I).     

Hydrothermal synthesis and characterization of a new organically templated three-dimensional open-framework gallium phosphate–phosphite (C6N2H18)2(C6N2H17)Ga15(OH)8(PO4)2(HPO4)12(HPO3)6·2H2O

Using H₃PO₃ as a phosphorus source and oxalic acid as a reducing agent, the first three-dimensional open-framework gallium phosphate–phosphite formula as (C₆N₂H₁₈)₂(C₆N₂H₁₇)Ga₁₅(OH)₈(PO₄)₂(HPO₄)₁₂(HPO₃)₆·2H₂O (1), has been hydrothermally synthesized in the presence of N,N,N′,N′-tetramethylenediamine (TMEDA) as a structure-directing agent. Compound 1 crystallizes in trigonal system with space group P ? 3, a = b = 19.046(3) Å, c = 8.3306(17) Å, γ = 120°, V = 2617.1(7) Å³, and Z = 1. Its 3-D network is based on alternated Ga-centered (GaO₄ tetrahedra, GaO₅ trigonal bipyramids, and GaO₆ octahedra) and P-centered (PO₄^3?, HPO₄^2?, and HPO₃^2?) units. Protonated organic amines and water molecules are located in the 12-membered ring channels.     

DNA Encapsulation of Ten Silver Atoms Produces a Bright, Modulatable, Near Infrared-Emitting Cluster

Photostability, inherent fluorescence brightness, and optical modulation of fluorescence are key attributes distinguishing silver nanoclusters as fluorophores. DNA plays a central role both by protecting the clusters in aqueous environments and by directing their formation. Herein, we characterize a new near infrared-emitting cluster with excitation and emission maxima at 750 and 810 nm, respectively that is stabilized within C(3)AC(3)AC(3)TC(3)A. Following chromatographic resolution of the near infrared species, a stoichiometry of 10 Ag/oligonucleotide was determined. Combined with excellent photostability, the cluster's 30% fluorescence quantum yield and 180,000 M(-1)cm(-1) extinction coefficient give it a fluorescence brightness that significantly improves on that of the organic dye Cy7. Fluorescence correlation analysis shows an optically accessible dark state that can be directly depopulated with longer wavelength co-illumination. The coupled increase in total fluorescence demonstrates that enhanced sensitivity can be realized through Synchronously Amplified Fluorescence Image Recovery (SAFIRe), which further differentiates this new fluorophore.     

Synthesis, characterization and applications of vinylsilafluorene copolymers: New host materials for electroluminescent devices

Vinylsilafluorene (VSiF) was successfully synthesized and copolymerized with vinylcarbazole and methyl methacrylate via free radical copolymerization for the first time. The synthesis, photophysical properties, computational modeling studies, and organic light-emitting devices of the VSiF copolymers were presented. The good coordinated photoluminescent (PL) spectra with the absorption of blue light-emitting materials and the high energy band-gap of the VSiF copolymers were observed. Higher triplet band gap (³ E _g) to host the blue phosphorescent emitters and better HOMO and LUMO than PVK for electron and hole injection and transportation of the VSiF model compounds were revealed by density functional theory (DFT) calculations. The preliminary device results in applications of these copolymers as host materials for green phosphorescent emitters demonstrate the copolymers of VSiF and vinylcarbazole have comparable device performance of polyvinylcarazole (PVK), suggesting a bright future of VSiF as building blocks for host materials.     

Julia烯烃合成法在天然产物全合成中的应用新进展

Julia烯烃合成法可通过使用不同芳杂基砜和控制反应条件等方法改变反应活性,提高反应立体选择性,从而使其在天然产物的全合成中得到重要的应用.综述了近年来Julia烯烃合成法(包括Julia-Lythgoe反应;Modified-Julia反应;Julia-kocieński反应)在天然产物全合成中的应用进展.     

含氢硅油-三氯化钌催化酰胺的还原反应研究

以原位形成的膦钌络合物为催化剂,研究了含氢硅油对酰胺的还原反应,考察了酰胺的结构、反应溶剂、配体等条件对催化反应的催化效率及产物结构的影响.仲胺基及伯胺的酰胺化合物被还原成相应的叔胺及仲胺;丙烯酰胺与含氢硅油反应时,选择性较差,得到丙烯腈、丙腈及与硅烷基相连的聚丙烯酰胺与聚丙烯腈.     

β-环糊精包覆碳纳米管基质用于氨基酸及小分子聚合物的MALDI-FT MS研究

制备了可用作氨基酸及小分子聚合物的MALDI-FTMS分析基质的β-环糊精包覆多壁碳纳米管.通过引入β-环糊精改善其碳纳米管亲水性.所制备的β-环糊精包覆多壁碳纳米管的扫描电镜图表明,该碳纳米管呈现纳米带状结构.与通常的氧化碳纳米管相比,所制备的β-环糊精改性CNT具有更低的背景信号.进一步采用氨基酸及聚乙二醇等小分子化合物对所制备的碳纳米管进行评价,得到很强的氨基酸及聚乙二醇的碱金属离子加合峰,表明该材料可使小分子化合物解吸离子化,且背景干扰小不会影响到小分子化合物检测.由此可见,制备的β-环糊精包覆多壁碳纳米管适于小分子化合物的MALDI-MS分析.     

An integrated on-chip sirtuin assay

A microchip-based assay to monitor the conversion of peptide substrates by human recombinant sirtuin 1 (hSIRT1) is presented. For this purpose a fused silica microchip consisting of a microfluidic separation structure with an integrated serpentine micromixer has been used. As substrate for the assay, we used a 9-fluorenylmethoxycarbonyl (Fmoc)-labeled tetrapeptide derived from the amino acid sequence of p53, a known substrate of hSIRT1. The Fmoc group at the N-terminus resulting from solid-phase peptide synthesis enabled deep UV laser-induced fluorescence detection with excitation at 266 nm. The enzymatic reaction of 0.1 U/μL hSIRT1 was carried out within the serpentine micromixer using a 400 μM solution of the peptide in buffer. In order to reduce protein adsorption, the reaction channel was dynamically coated with hydroxypropylmethyl cellulose. The substrate and the deacetylated product were separated by microchip electrophoresis on the same chip. The approach was successfully utilized to screen various SIRT inhibitors.     

Molecularly imprinted polymer coated on stainless steel fiber for solid-phase microextraction of chloroacetanilide herbicides in soybean and corn

A molecularly imprinted polymer (MIP) with metolachlor as template was firstly coated on stainless steel fiber through chemical bonding strategy to solve the fragility problem of silica fiber substrate for solid-phase microextraction. The surface pretreatment of stainless steel fiber and the polymerization conditions were investigated systematically to enhance the preparation feasibility and MIP coating performance, and then a porous and highly cross-linked MIP coating with 14.8-μm thickness was obtained with over 200 times re-usability which was supported by non-fragile stainless steel fiber adoption. The MIP coating possessed specific selectivities to metolachlor, its metabolites and other chloroacetanilide herbicides with the factors of 1.1–4.6. Good extraction capacities of metolachlor, propisochlor and butachlor were found with MIP coating under quick adsorption and desorption kinetics, and the detection limits of 3.0, 9.6 and 38 μg L⁻¹ were achieved, respectively. Moreover, the MIP-coated stainless steel fiber was evaluated for trace metolachlor, propisochlor and butachlor extraction in the spiked soybean and corn samples, and the enrichment factors of 54–60, 27–31 and 15–20 were obtained, respectively.     

Synthesis and characterization of Poly(N-isopropylacrylamide)/Poly(acrylic acid) semi-IPN nanocomposite microgels

A novel pH- and temperature-sensitive nanocomposite microgel based on linear Poly(acrylic acid) (PAAc) and Poly(N-isopropylacrylamide) (PNIPA) crosslinked by inorganic clay was synthesized by a two-step method. First, PNIPA microgel was prepared via surfactant-free emulsion polymerization by using inorganic clay as a crosslinker, and then AAc monomer was polymerized within the PNIPA microgel. The structure and morphology of the microgel were confirmed by FTIR, WXRD and TEM. The results indicated that the exfoliated clay platelets were dispersed homogeneously in the PNIPA microgels and acted as a multifunctional crosslinker, while the linear PAAc polymer chains incorporated in the PNIPA microgel network to form a semi-interpenetrating polymer network (semi-IPN) structure. The hydrodynamic diameters of the semi-IPN microgels ranged from 360 to 400 nm, which was much smaller than that of the conventional microgel prepared by using N,N′-methylenebis(acrylamide) (MBA) as a chemical crosslinker, the later was about 740 nm. The semi-IPN microgels exhibited good pH- and temperature-sensitivity, which could respond independently to both pH and temperature changes.