A versatile access to new halogenated 7-azidocoumarins for photoaffinity labeling: Synthesis and photophysical properties

A versatile methodology for the synthesis of 6/8-halogenated 7-aminocoumarins from the corresponding 7-hydroxy analogs using Pd-catalyzed amination reaction as the key step is presented. Further readily conversion into 7-azidocoumarins was performed and the resulting aryl azides proved higher stability and reactivity than the corresponding non-halogenated parent compound. These new compounds may thus constitute attractive scaffolds for designing novel photoaffinity reagents for various challenging bio-labeling applications.     

A new photoactive building block for investigation of DNA backbone interactions: photoaffinity labeling of human DNA polymerase beta

The cross-linking of target proteins or nucleic acids to light-activatable ligands is an important tool for elucidating molecular interactions. Through the use of photoaffinity-labeling reagents, several new insights into nucleic acid interactions have been obtained, for example in DNA replication and repair. In most known photoprobes, the applied light-sensitive functionalities are placed directly at the nucleobase or are attached via linkers to either the nucleobase or the phosphate backbone. Here we describe the first photoprobe that bears a light-sensitive aryl(trifluoromethyl)diazirine at the sugar moiety of a DNA oligonucleotide. We devised a route for the synthesis of the modified nucleoside and its incorporation into an oligonucleotide. The photoactive species was proven to be stable under the conditions employed in routine automated DNA synthesis. The modified oligonucleotide was shown by subsequent photolabeling studies of human DNA polymerase beta to form a covalent complex to the enzyme upon irradiation with near-UV light.     

A new Li-based ceramic of Li4MgSn2O7: Synthesis,phase evolution and microwave dielectric properties

A pure-phase Li₄MgSn₂O₇ (L₄MS) was successfully synthesized through optimizing the calcination condition. Microwave dielectric properties of the L₄MS ceramic with the phase evolution were investigated together with its low-temperature sintering. The sample maintains a single L₄MS phase as sintered below 1200?°C, such that τ_f remains a constant value of ～12.4?ppm/°C. Accompanied by the appearance of impurity phases (Li₂SnO₃)_ss and especially (MgO)_ss at higher sintering temperatures, excellent microwave dielectric properties of ε_r?=?13.1–13.5, Q?×?f?=?106,800–126,810?GHz and τ_f ?=?0–?4.2?ppm/°C are obtained in samples sintered at 1215–1260?°C for 4?h. Reduction of sintering temperature using LiF sintering aid also helps achieve pure-phase dense L₄MS ceramic. The L₄MS?+?x wt.% LiF ceramic exhibits ε_r～13.7, Qxf～97,000?GHz (x?≤?3) and τ_f ～8–13?ppm/°C sintered at 850?°C for potential LTCC applications, and ε_r ～13.9, Qxf～146,000?GHz and τ_f ～1.5–6?ppm/°C (x?≥?4) as sintered 1000?°C, exhibiting large potentials for microwave dielectric candidates.     

A new Schiff base: Synthesis,characterization and optimization of metal ions-binding properties

In this study, a new Schiff base (H₄TSTE) was synthesized and characterized by elemental analysis, FT-IR, NMR and MS spectral data. Liquid–liquid extraction process was performed for removal of Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) from aqueous solutions by means of H₄TSTE. The extractions were investigated depending on the concentration of picric acid, metal ion and H₄TSTE ligand. Response surface methodology (RSM) was first applied to optimize metal ion-binding properties of H₄TSTE. The extraction efficiency was estimated to be >98% for all metals by models. Under the same conditions, the extraction efficiency was experimentally found to be >97% with a relative standard deviation within ±0.10 (N = 4), indicating the suitability of the models.     

Synthesis, characterization and photophysical properties of novel fluorene-based copolymer with pendent urea group: Fluorescent response for anions through H-bonding interaction

A novel fluorene-based copolymer P₁ with diphenyl urea as pendent group, as well as its analogous copolymer P₂ without urea group for comparison, were synthesized by Suzuki-coupling reaction, and characterized by ¹H NMR, EA, IR and GPC. The polymers were brightly blue emissive in THF, DMF, or DMSO solution. Anion titration experiments carried out in THF indicate that the polymer P₁ has good selectivity for fluoride ion, acetate ion, and dihydrogen phosphate ion, and the sensitivity and selectivity of P₁ toward these anions come from the strong hydrogen-bond interaction between the anions and the urea group of the copolymer. This new system utilizing the strong luminescence property of the polyfluorene as reporter and the hydrogen-bond-forming ability of urea group may act as novel effective anions receptor and chemosensor.     

A new molybdate host material: Synthesis,upconversion, temperature quenching and sensing properties

A new upconversion (UC) host material YbMoO₄ with 0–100 mol% Er³⁺ doping was obtained using a facile coprecipitation method. A pure tetragonal phase of YbMoO₄ was synthesized, which was dependent on the pH value of the reaction mixture and the sintering temperature. The existence of pentavalent molybdenum was confirmed in YbMoO₄ by thermal-reduction of hexavalent molybdenum. Under a 976 nm laser diode excitation, both green and red UC emissions were observed from Er³⁺:YbMoO₄, which corresponded to the ²H_11/2/⁴S_3/2→⁴I_15/2 and ⁴F_9/2→⁴I_15/2 transitions of Er³⁺ with the strongest luminescence appearing at a mole ratio of Er:Yb=1:10. The two-photon absorption UC process was responsible for the green and red emissions. The temperature-dependent green UC emission of Er³⁺:YbMoO₄ was observed, which was rationalized using the thermal quenching model. The fluorescence intensity ratio (FIR) of green UC emissions was studied as a function of temperature and its high thermal sensitivity implied that the Er³⁺:YbMoO₄ material is a promising prototype for applications in optical temperature sensing.     

A new family of Cu-doped lanthanum silicate apatites as electrolyte materials for SOFCs: Synthesis,structural and electrical properties

La_9.67Si_6-xCu_xO_26.5-x (LSC, x = 0, 0.1, 0.3 and 0.5) are synthesized by a citric-nitrate method. Substitution Si with Cu promotes the densification process of silicate apatite. Unit cell parameters and volume increase linearly with Cu content. The Rietveld refinement reveals a much more distorted (Si,Cu)O₄ tetrahedra in the oxygen stoichiometric La_9.67Si_5.5Cu_0.5O₂₆ sample. The structural observation from high temperature XRD implies a second-order phase transition in La_9.67Si_5.5Cu_0.5O₂₆. Cu-doping decreases the activation energy of oxygen ion conduction and increases the conductivity of LSC materials in the temperature range of 550–800 °C. La_9.67Si_5.5Cu_0.5O₂₆ shows the conductivity values of 29.3 and 12.3 mS cm⁻¹ at 800 °C and 650 °C, respectively. The oxygen ion transference number of La_9.67Si_5.5Cu_0.5O₂₆ is higher than 0.99. These attractive properties make the La_9.67Si_5.5Cu_0.5O₂₆ a promising oxygen ion conducting electrolyte for applications of solid oxide fuel cells, oxygen sensors, oxygen separation membranes, etc.     

Bottom-up and new compaction processes: A way to tunable properties of nanostructured cobalt ferrite ceramics

In this work we describe a novel bottom-up strategy to process cobalt ferrite CoFe₂O₄ nanostructured bulk material. This strategy offers the possibility to drive their magnetic and mechanical properties in a wide range of different behaviors. In particular, we show how to tune the blocking temperature along with optimized mechanical strength. This method combines forced hydrolysis in polyol, a soft chemistry route, and Spark Plasma Sintering (SPS) for consolidation. To highlight this method, we also performed compaction by a standard Hot Isostatic Pressing (HIP) process. Thus we compare the nanostructured bulk microstructures (for both compaction techniques) and magnetic static properties to those of several CoFe₂O₄ nanopowder samples showing particle size and annealing temperatures comparable to those of the nanostructured bulk samples. Microstructure, radio-crystallographic and magnetic studies have been carried out in order to show the optimization of the processing strategy in this work.     

A proposed mechanism for the reductive ring opening of the cyclodiphosphate MEcPP, a crucial transformation in the new DXP/MEP pathway to isoprenoids based on modeling studies and feeding experiments

Experimental and theoretical investigations concerning the second-to-last step of the DXP/MEP pathway in isoprenoid biosynthesis in plants are reported. The proposed intrinsic or late intermediates 4-oxo-DMAPP (12) and 4-hydroxy-DMAPP (11) were synthesized in deuterium- or tritium-labeled form according to new protocols especially adapted to work without protection of the diphosphate moiety. When the labeled compounds MEcPP (7), 11, and 12 were applied to chromoplast cultures, aldehyde 12 was not incorporated. This finding is in agreement with a mechanistic and structural model of the responsible enzyme family: a three-dimensional model of the fragment L271-A375 of the enzyme GcpE of Streptomyces coelicolor including NADPH, the Fe(4)S(4) cluster, and MEcPP (7) as ligand has been developed based on homology modeling techniques. The model has been accepted by the Protein Data Bank (entry code 1OX2). Supported by this model, semiempirical PM3 calculations were performed to analyze the likely catalysis mechanism of the reductive ring opening of MEcPP (7), hydroxyl abstraction, and formation of HMBPP (8). The mechanism is characterized by a proton transfer (presumably from a conserved arginine 286) to the substrate, accompanied by a ring opening without high energy barriers, followed by the transfer of two electrons delivered from the Fe(4)S(4) cluster, and finally proton transfer from a carboxylic acid side chain to the hydroxyl group to be removed from the ligand as water. The proposed mechanism is in agreement with all known experimental findings and the arrangement of the ligand within the enzyme. Thus, a very likely mechanism for the second to last step of the DXP/MEP pathway in isoprenoid biosynthesis in plants is presented. A principally similar mechanism is also expected for the reductive dehydroxylation of HMBPP (8) to IPP (9) and DMAPP (10) in the last step.     

A new intumescent flame retardant containing phosphorus and nitrogen: Preparation,thermal properties and application to UV curable coating

A novel intumescent flame retardant piperazine-N,N′-bis(acryloxyethylaryl-phosphoramidate) (N-PBAAP) containing phosphorus and nitrogen used for UV curable coating was synthesized and characterized by Fourier transform infrared spectrometry (FTIR), ¹H and ³¹P nuclear magnetic resonances (NMRs). The thermal degradation and volatilized products of the N-PBAAP cured film were monitored by real time Fourier transform infrared (RT-FTIR) and thermal gravimetric-Fourier transform infrared (TG-FTIR) technique, respectively. Scanning electron microscopy (SEM) was employed to investigate the surface morphology of the residual char. And possible mechanism for the thermal degradation of N-PBAAP film was proposed. To investigate the flame retardancy of N-PBAAP in UV curable coatings, a series of UV curable intumescent flame retardant resins were obtained by blending N-PBAAP with EA (epoxy acrylate oligomer) in different ratios. The flammability and thermal properties of the cured films were studied by Microscale Combustion Calorimeter (MCC) and thermogravimetric analysis (TGA). In MCC test, the peak heat release rates (pHRRs) of the blends were all lowered by the addition of N-PBAAP comparing with the pure EA. And TG results revealed that N-PBAAP can greatly enhance the char residues of EA films at high temperature region.     

Synthesis and properties of 4‐(ω‐methoxyoligodimethylsiloxanyl)butyl maleate: A new surfmer

Anionic reactive maleate with hydrophobic oligosiloxane chain was synthesized to use as a stabilizer in the batch and seeded emulsion polymerization of traditional monomers (acrylates, methacrylates, styrene, etc.). Polymerizable surfactant is obtained in a three‐step synthesis, starting from the anionic polymerization of cyclic siloxanes, followed by the silylation of methanol with the obtained cyclic oligomer, and finishing with the acylation of the linear oligomer by maleic anhydride. The improved technique of the synthesis of 4‐chlorobutoxydimethylchlorosilane, one of the initial substances for obtaining siloxane monomer, was elaborated. The anionic polymerization of octamethylcyclotetrasiloxane using cyclic alkoxysilane was carried out to form siloxane cyclic oligomer for the first time. The chemical structure of the monomer synthesized was confirmed by IR spectroscopy and functional analysis. Critical micelle concentration of the obtained surfactant was measured. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 310–313, 2004     

A new homologous series of linear aliphatic unsaturated hydroxypolyesters a polyol soft segments for polyurethanes: Synthesis and characterization

Synthesis and characterization of a new series of low molecular weight (MW = 500–3000) OH-terminated linear aliphatic unsaturated polyesters based on cis-2-butene-1,4-diol and oxalic to sebacic acid were investigated. Direct polycondensation and transesterification methods were used for the syntheses. The latter was recognized to be the preferable method due to its lower reaction temperature and time, lower diol/diacid ratio, absence of decarboxylation, and formation of a product with low polydispersity (M _w/M _n = 1.3–2.7). Elemental analysis, GPC, FTIR, ¹H-NMR, DSC, and WAXD were used for the investigations. A segmented polyurethane based on poly (cis-2-butylene adipate) glycol was also synthesized and spectroscopically identified. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 173–183, 1998     

Synthesis and properties of uniform beads based on macroporous copolymer glycidyl methacrylate–ethylene dimethacrylate: A way to improve separation media for HPLC

Monodisperse beads based on hydrolyzed macroporous poly(glycidyl methacrylate-co-ethylene dimethacrylate) for use as size-exclusion HPLC packings were synthesized by the method of “activated” swelling of polystyrene seeds followed by a suspension polymerization of both methacrylates. Effects of the type and fraction of the swelling agent, inert porogenic solvent, and cross-linking monomer on the uniformity of the particles, extent of the specific surface area, pore volume, pore size, and pore-size distribution and chromatographic properties (size-exclusion limit and column effciency) have been investigated. Trends leading to the synthesis of macroporous particles with predesigned properties for use in size-exclusion high-performance liquid chromatography in both aqueous and organic mobile phase were studied. © 1992 John Wiley & Sons, Inc.     

A novel far-red phosphors Li2ZnTi3O8:Cr3+ for indoor plant cultivation:Synthesis and luminescence properties

A novel far-red phosphors Li₂ZnTi₃O₈:Cr³⁺ were successfully synthesized via the conventional solid-state method. The structural characteristics, luminescence properties and concentration quenching of the Li₂ZnTi₃O₈:Cr³⁺ phosphors were investigated systematically. Under the excitation at 360 nm and 468 nm, the Li₂ZnTi₃O₈:Cr³⁺ phosphors displays the emission spectra in the range from 600 nm to 850 nm. The far-red emission centered at 735 nm was attributed to the spin-forbidden ²E→⁴A₂ transition of Cr³⁺ ions. The research results of this paper indicate that the phosphors Li₂ZnTi₃O₈:Cr³⁺ has prospective applications in indoor plant cultivation.     

Eu2+ activated NaBa3Si2O7F: A new efficient blue-emitting luminescent material for solid-state lighting and display

Exploring novel efficient phosphors for lighting and display has always been an important and meaningful work for researchers. Herein, a novel efficient blue-emitting phosphor, Eu²⁺ doped barium-containing silicate fluoride NaBa₃Si₂O₇F, was prepared by solid-state method. The phosphor can produce bright blue light peaked at 452 nm with full-width at half-maximum about 57 nm under near-UV light excitation, and it exhibits a high internal quantum yield about 76.23%. The temperature-dependent photoluminescence spectra show that this phosphor owns good thermal stability, and the emission intensity at 425 K is 67% of that at room temperature. The outstanding data of fabricated device demonstrate that the blue phosphor has large possibility of practical application for white light-emitting diode. Furthermore, the phosphor also possesses good cathodoluminescence properties under various accelerating voltage with different probe currents, indicating its potential application in field emission displays.     

A Review of Molybdenum Catalysts for Synthesis Gas Conversion to Alcohols: Catalysts,Mechanisms and Kinetics

Recent literature on synthesis gas conversion to higher alcohols over Mo-based catalysts is reviewed. Density functional theory calculations show that Mo-CO adsorption is weakened by C, P, or S ligands and this facilitates CO dissociation, either directly on Mo₂C, or by H-assisted dissociation on MoS₂, Mo₂C, and MoP. Consequently, Mo-based catalysts have high hydrocarbon selectivity unless they are promoted with alkali metals and/or Group VIII metals. Promoted MoS₂ and MoP have alcohol selectivities of ～80 C atom % (CO₂-free basis) at typical operating conditions (5–8 MPa, H₂/CO = 2–1, 537–603 K), whereas on promoted Mo₂C, alcohol selectivities are ～60%. The kinetics of the synthesis gas conversion reactions over Mo-based catalysts have mostly been described by empirical power law models and the alcohol and hydrocarbon product distributions are consistent with a CO insertion mechanism for chain growth.     

Green esterification: A new approach to improve thermal and mechanical properties of poly(lactic acid) composites reinforced by cellulose nanocrystals

Cellulose nanocrystal (CNCs)‐reinforced poly(lactic acid) (PLA) nanocomposites were prepared using twin screw extrusion followed by injection molding. Masterbatch approach was used to achieve more efficient dispersion of CNCs in PLA matrix. Modified CNCs (b‐CNCs) were prepared using benzoic acid as a nontoxic material through a green esterification method in a solvent‐free technique. Transmission electron microscopy images did not exhibit significant differences in the structure of b‐CNCs as compared with unmodified CNCs. However, a reduction of 6.6–15.5% in the aspect ratio of b‐CNCs was observed. The fracture surface of PLA‐b‐CNCs nanocomposites exhibited rough and irregular pattern which confirmed the need of more energy for fracture. Pristine CNCs showed a decrease in the thermal stability of nanocomposites, however, b‐CNCs nanocomposites exhibited higher thermal stability than pure PLA. The average storage modulus was improved by 38 and 48% by addition of CNCs and b‐CNCs in PLA, respectively. The incorporation of b‐CNCs increased Young's modulus, ultimate tensile stress, elongation at break, and impact strength by 27.02, 10.90, 4.20, and 32.77%, respectively, however, CNCs nanocomposites exhibited a slight decrease in ultimate strength and elongation at break. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46468.     

A new approach to artificial and modified proteins: theory-based design, synthesis in a cell-free system and fast testing of structural properties by radiolabels

A novel approach to the creation of artificial and modifiedproteins has been elaborated. The approach includes a sequencedesign based on the molecular theory of protein secondary structureand folding patterns, gene expression in a cell-free systemand testing of structural properties of the synthesized polypeptidesat a nanogram level using radiolabelled chains. The approachhas been applied to a new synthetic protein albebetin whichhas been designed to form a 3-D fold which does not contradictany structural rule but has been never observed up to now innatural proteins. Using size-exclusion chromatography, urea-gradientelectrophoresis and limited proteolysis of a radiolabelled chain,it has been shown that the artificial protein is nearly as compactas natural proteins, cooperatively unfolds at high urea concentrationsand has some structural features of a definite structure consistentwith the designed one. As albebetin has been designed as consistingof two structural repeats, a ‘halfalbebetin’ (oneof these repeats) has also been synthesized and studied. Itwas shown that ‘half-albebetin’ is also compact     

A new heptamolybdate-based supramolecular compound with an alternating organic and inorganic layer structure: Synthesis,crystal structure and properties of (Hapy)4[Co(H2O)5Mo7O24] · 9H2O

A new supramolecular compound based on the heptamolybdate anion, formulated as (Hapy)₄[Co(H₂O)₅Mo₇O₂₄] · 9H₂O (1) (apy = 2-aminopyridine), has been synthesized hydrothermally and characterized by elemental analyses, IR, and X-ray single crystal diffraction. Compound 1 crystallizes as alternating layers of inorganic anions and organic cations linked by hydrogen-bonding interactions. A variable-temperature magnetic susceptibility measurement of 1 demonstrated the presence of antiferromagnetic interactions. Furthermore, the cyclic voltammogram of 1 shows two reversible redox couples both of which are associated with two-electron processes of molybdenum.