Two structural analogous TbIII-indazole-radical complexes with different dynamic magnetic behaviors

The combination of Tb^III ion with two different indazole nitronyl nitroxide radicals resulted in two novel 2p-4f compounds, namely, [Tb(hfac)₃(5-IndazoleNIT)]₂ (1) (hfac = hexafluoroacetylacetone; 5-IndazoleNIT = 5-(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl- 4,5-hydro-1H-imidazol-2-yl)-1H-indazole) and [Tb(hfac)₃(6-IndazoleNIT)]₂ (2) (6-IndazoleNIT = 6-(1′-oxyl-3′-oxido-4′,4′,5′,5′-tetramethyl- 4,5-hydro-1H-imidazol-2-yl)-1H-indazole). Single crystal X-ray diffraction studies revealed that compound 1 was binuclear complex, in which each 5-IndazoleNIT molecular acted as a bridging ligand linking two Ln^III ions through its oxygen atom of the NO group and nitrogen atom of the indazole ring to form a cyclic four-spin system. Complex 2 exhibited analogous binuclear cyclic four-spin systems with different space group. Compound 1 was found to take on slow relaxation of the magnetization, suggesting single-molecule magnet (SMM) behavior, while no ac signal is noticed for compound 2. The different magnetic relaxation behaviors between 1 and 2 are due to the different location of the radical in the indazole ring. It is demonstrated that the location of the radical in the indazole ring played an important role in determining the spin dynamic for the lanthanide-radical system.     

Two 2-D homometallic and heterometallic Schiff-base complexes bridged by dicyanamide

Two Schiff-base complexes composed of homometallic and heterometallic dinuclear units, [Zn₂(salpn)]²⁺ and [CuCd(salpn)]²⁺, have been prepared and characterized. The dinuclear second building units are connected by dicyanamide (dca) ligands, forming 2-D layer structure. Zinc(II) complex displayed structure-related photoluminescence properties in the solid state.     

Synthesis and properties of new novolacs based on heteroatom‐bridged phenol derivatives

We describe the synthesis and properties of new novolacs prepared by addition‐condensation of heteroatom‐bridged phenol derivatives and formaldehyde. The trifluoroacetic acid‐catalyzed polymerization of equimolar amounts of bis(4‐methoxyphenyl) ether ( 1a ) and formaldehyde proceeded homogeneously to afford the polymer ( 2a ) in 49% yield (M_n 2600, M_w/M_n 1.8). From the FTIR, ¹H‐NMR, and ¹³C‐NMR spectra of 2a , it was evident that the polymer had methylene moieties‐bridged repeating units in the polymer backbone. A higher molecular weight novolac ( 2a ′) (yield 99%, M_n 16,600, M_w/M_n 12.9) could be prepared by using an excess of formaldehyde. Bis(4‐methoxyphenyl) sulfone novolac ( 2b ) (M_n 1300, M_w/M_n 1.2) and bis(4‐methoxyphenyl) sulfide novolac ( 2d ) (M_n 1200, M_w/M_n 1.9) were also prepared. However, the polymerization of bis(4‐hydroxyphenyl) sulfone ( 1c ) did not proceed, even when it was attempted under various reaction conditions. From TGA, the temperatures at 10% loss in weight (T₁₀) for 2a , 2a ′, and 2b were found to be 413, 430 and 393°C, respectively. These results suggested that heteroatom‐bridged novolacs based on phenol derivatives have good thermal stability than other organosoluble polymers; moreover, these novolacs could be expected to function as processable materials, polymer blends for engineering plastics, etc. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Specific features of the relaxation processes in As2Se3 films prepared by different methods

The specific features of the processes of charge transfer and accumulation in thin films of arsenic triselenide As₂Se₃ are investigated by measuring the isothermal relaxation of dark electric currents. It is established that the relaxation properties of the films substantially depend on the method used for their preparation, which, apparently, can be associated with the structural features of this class of materials. Moreover, it is confirmed that the relaxation of the electric current in the films of chalcogenide glasses under investigation occurs through a non-Debye mechanism, irrespective of the preparation technique.     

ZrO2-8mol%Dy2O3固体电解质燃料电池性能

将强碱介质中用水热法合成的立方相ZrO2-8mol％Dy2O3纳米晶在较低的温度（1400℃）下烧结,制得了导电性固体电解质陶瓷样品。以该陶瓷作为固体电解质,Pt作电极材料组成氢．空气燃料电池,测定了不同pH介质中水热反应产物纳米晶的陶瓷样品在800～1000℃下的燃料电池性能。结果表明,该系列陶瓷样品的燃料电池均具有稳定的放电性能,燃料电池的短路电流密度随着水热反应介质pH值的减小而增大。在该系列陶瓷中,水热反应介质pH=9．95的陶瓷样品的燃料电池性能最高,在1000℃下,其短路电流密度为320mA／cm^2。     

Syntheses,structures and magnetic properties of two Dy6 clusters based on polydentate ligands with a new topological motif

Two novel analogous Dy₆ complexes were synthesized in low-temperature reactions and characterized via X-ray crystallographic and magnetic measurements. Structural analysis revealed the resulting complexes form a new topological motif for hexanuclear dysprosium clusters. Magnetic studies indicated the two complexes are both ferromagnetic interactions and exhibit magnetization relaxation behavior.     

基于不同粒径ZIF-8多孔液体的二氧化碳捕集性能

通过粒径调控策略制备了基于不同粒径ZIF-8的多孔液体(PLs),并用于CO₂的捕集。考察了ZIF-8粒径对多孔液体捕集CO₂的吸附容量、吸附速率、CO₂/N₂选择性及循环稳定性的影响,并对不同粒径多孔液体的CO₂吸附动力学进行研究。结果表明,多孔液体中具有永久的孔隙结构,不同多孔液体均具有优异的流动性。3种不同粒径的多孔液体室温下放置60 d或4500 r/min下离心5 min后均未出现聚集、沉积现象,表明不同粒径多孔液体均具有较好的稳定性。由不同粒径ZIF-8合成的多孔液体对CO₂的吸附过程包括物理吸附和化学吸附。其中,ZIF-8粒径为43 nm的多孔液体ZIF-8-PLs(43)对CO₂的饱和吸附容量最大,为63.0 mg/g;ZIF-8-PLs(145)展现了较快的CO₂吸附速率,准二级动力学常数为1.91×10^–3 g/(mg·min);ZIF-8-PLs(1400)具有最高的C...     

Phenoxo-O bridged dinuclear lanthanide complexes based on a multitooth Schiff base ligand: Structures,fluorescence properties and single-molecule magnet behavior

Two Ln(III) complexes, [Tb(dbm)L(CH₃)₂CHOH]₂·4(CH₃)₂CHOH (1) and [Dy(dbm)L(CH₃)₂CHOH]₂ (2) (dbm = 1,3-diphenyl-1,3-propanedione, HL = N-(methylene-8-hydroxyquinoline)-2-furohydrazide), have been synthesized, structurally and magnetically characterized. Both 1 and 2 are phenoxo-O bridged binuclear complexes, in which Ln1 and Ln1a are in an eight-coordinated environment bridged by two phenoxido oxygen atoms of two 8-hydroxyquinoline Schiff-base ligands. Magnetic studies reveal that 2 demonstrates single-molecule magnet behavior. In addition, the luminescence properties of 1 and 2 were studied.     

钐、镝-2-噻吩甲酸-2,2'-联吡啶三元配合物的合成及Dy3+的荧光性质研究

合成了钐、镝与2-噻吩甲酸-2,2'-联吡啶的三元配合物.通过元素分析、稀土配合滴定及TG-DTG分析,确定了配合物组成为:REL3L'·C2H5OH(RE=Sm,Dy;L=2-噻吩甲酸,L'=2,2'-联吡啶);摩尔电导数据表明,此配合物为非电解质;测定了配体及配合物的红外光谱,表明配体2-噻吩甲酸中的羧基氧与稀土离子配位,2,2'-联吡啶上两个氮原子与稀土离子配位.还研究了Dy3 配合物的荧光激发和发射光谱.     

Two Gd2 compounds constructed by 8-hydroxyquinoline Schiff base ligands: Synthesis,structure, and magnetic refrigeration

Two new Gd₂ compounds having formulae, [Gd₂(hfac)₄(L1)₂] (1) and [Gd₂(hfac)₄(L2)₂] (2) (hfac = hexafluoroacetylacetonate, HL1 = 2-[4-methylaniline-imino]methyl]-8-hydroxyquinoline and HL2 = 2-[(3,4-dimethylaniline)-imino]methyl]-8-hydroxyquinoline), have been successfully synthesized via applying two different 8-hydroxyquinoline Schiff base ligands, and further characterized by crystallography. Structural analysis shows that both of 1 and 2 are phenoxo-O bridged dinuclear complexes. The magnetic study reveal that 1 and 2 display cryogenic magnetic refrigeration properties with maximum − ΔS_m = 17.66 J kg^− 1 K^− 1 at 2 K and 7 T for 1 and − ΔS_m = 14.81 J kg^− 1 K^− 1 at 3 K and 7 T for 2.     

New stabilizers for polystyrene based on 2-thioacetic acid benzothiazol complexes

The photostabilization of polystyrene (PS) films by 2-thioacetic acid benzothiazol with Sn(II), Cd(II), Ni(II), Zn(II), and Cu(II) complexes was investigated. The PS films containing complexes of concentration 0.5% by weight were produced by the casting method from chloroform solvent. The photostabilization activities of these compounds were determined by monitoring the carbonyl and hydroxyl indices with irradiation time. The changes in viscosimetric average molecular weight of PS with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (ϕ_cs) of these complexes in PS films was evaluated and found to range between 3.60 × 10⁻⁶ and 7.78 × 10⁻⁶. The results obtained showed that the rate of photostabilization of PS in the presence of the additive is in the following trend: Ni(L)₂ > Cu(L)₂ > Zn(L)₂ > Cd(L)₂ > Sn(L)₂. According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among UV absorption, peroxide decomposer and radical scavenger for photostabilizer additive mechanisms were suggested. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,structures, and magnetic properties of tetranuclear nickel and cobalt complexes with 2-mercaptobenzoxazole

The synthesis and magnetic properties of two tetranuclear Ni complex Ni₄(L)₄(CH₃CN)₄(OCH₃)₄ 1 and Co complex Co₄(L)₄(CH₃CN)₄(OCH₃)₄ 2 (HL = 2-mercaptobenzoxazole) are reported. The X-ray structures reveal that 1 and 2 are isostructural with [Ni₄O₄] 1 and [Co₄O₄] 2 cubane-like cores. Analysis of the temperature dependent magnetic measurements data shows that both complexes are paramagnetic with weak antiferromagnetic coupling. One-J model and two-J model are both applied to fit the experimental magnetic data of 1 and the results indicate the exchange coupling between the type A Ni(II) ions affected by NCS three atoms bridge in 2-mercaptobenzoxazole ligand.     

Syntheses,structures and magnetic properties of a series of lanthanide complexes based on p-methoxybenzoic acid

A new series of lanthanide metal complexes [Ln(L)₃]_n (L = p-methoxybenzoic acid, Ln = Pr 1, Eu 2, Tb 3, Dy 4, Ho 5, Er 6, Yb 7) have been synthesized under hydrothermal conditions. Single-crystal X-ray diffraction measurements reveal that these compounds are isostructural, crystallizing in the monoclinic space group P2₁/c and giving 1D chain structures. Magnetic studies reveal antiferromagnetic behavior for complexes 1, 3, 5 and 6, ferromagnetic behavior for complex 4 and spin-canting behavior for 7.     

Dielectric studies of cellulose and its derivatives: 2. Effects of pressure and temperature on relaxation behaviour

Dielectric and water absorption measurements are reported for cellulose acetate, a plasticized cellulose acetate and ethyl cellulose as a function of pressing temperature and pressure. The observed effects are explained on the basis that the work done in producing the discs used in these measurements destroys residual fibre structure and leads to an increase in the dipolar activity of the sample. The observation of gelatinization is discussed in terms of the effects on the side chain mobility and the densification of the polymer matrix. The effects observed in the case of dibutylphthalate are in agreement with data from other measurements on another cellulose derivative and indicate strong interactions between the plasticizer and the polymer. Water absorption data also reflects the changes which occur in the morphology with changes in the pressing conditions.     

不同磁化率粒子在磁场流分离中保留行为的研究

缺乏针对不同磁化率粒子的分离技术成为制约磁性药物制剂研究发展的重要因素。讨论了利用螺旋毛细管作为分离通道的简单场流分离装置,对不同磁化率的磁性粒子进行分离的可行性,并对影响分离的条件进行了考察。结果表明,在旋转频率为2.21 Hz,流速为0.16 mL/min,磁场距离为0.48 mm的条件下,旋转磁场流分离体系可以很好的分离不同磁化率的磁性粒子。旋转磁场的引入和水动抬升力的作用克服了固定磁场作用范围有限和粒子团聚等缺点,使此方法具有较高的分离度。     

A new Zn2+ chemosensor based on functionalized 8-hydroxylquinoline

A new fluorescent Zn²⁺ chemosensor (3) based on functionalized 8-hydroxylquinoline has been synthesized and characterized. Compound 3 shows weak fluorescence in CH₃CN–HEPES buffer solution (50 mM, pH 7.2 v/v = 1:9), but the fluorescence is significantly enhanced upon binding to Zn²⁺ through a zinc(II)-catalyzed ester hydrolysis reaction to form a highly emissive zinc(II) complex. This suggests that 3 can be served as a typical “switch–on” chemosensor with high selectivity for Zn²⁺ over other metal ions.     

Two novel lead-carboxylate complexes based on nicotinic acid N-oxide: Synthesis,crystal structures and luminescent properties

Two new lead-carboxylate complexes based on nicotinic acid N-oxide ligand, [Pb(NNO)(FA)_0.5] (1) (HNNO = nicotinic acid N-oxide, FA = fumaric acid) and [Pb₂(NNO)(BTC)] (2) (H₃BTC = 1,3,5-benzenetricarboxylic acid) were hydrothermally synthesized and characterized by the elemental analyses, IR spectra and single crystal X-ray diffraction. Significant phosphorescent properties of two compounds were observed at room temperature.     

Study on synthesis and photoactivity of N-substituted diazabicyclononane derivatives with different substituents

N-substituted diazabicyclononanes with different benzylic substituents were synthesized by hydrogenating diazabicyclononene with LiAlH₄ and alkylating secondary amine with halobenzyl derivatives. The synthesized diazabicyclononanes were identified with NMR spectrometry; the UV absorption and fluorescence emission of the diazabicyclononanes were examined with spectroscopes; the reactivity of the diazabicyclononane as radical photoinitiator and photolatent base were evaluated with DSC, FTIR spectroscope and gel fraction determination; the effects of substituents on the photoactivities of the diazabicyclononanes were investigated. Electron conjugation in the substituents played a prominent role on the photoactivity. As the conjugation extended, the extinction coefficient increased and fluorescence decreased; meanwhile, the UV absorption expanded towards low frequency. For diazabicyclononane N-substituted with 4-methylene benzophenone, the maximum absorption appeared around 256 nm with extinction coefficient 1.78×10⁴⁻ mol⁻¹ L cm⁻¹. It could work as radical photoinitiator and photolatent base simultaneously. With this diazabicyclononane, epoxy acrylate could be UV cured within seconds and the activation temperature of epoxy/anhydride could be reduced 50 °C after UV excitation. The gel fraction of acrylate/epoxy hybrid resins could be about 90% after UV-thermal dual curing.     

Spectroscopic features and reactivity of CO adsorbed on different Au/CeO2 catalysts

An FTIR study of CO adsorption from 120 K up to room temperature on a series of Au–ceria samples is presented. Samples with low gold content (0.7 and 0.6 at%) were prepared by urea gelation/co-precipitation and by cyanide leaching of the high-gold content (5.8 at%) material prepared by deposition–precipitation on La-doped CeO₂. The samples were subjected to different pretreatments to collect information on the surface composition under working conditions. An absorption band at 2130–2140 cm⁻¹, not reversible on outgassing and more resistant to oxidation than the usual carbonyl band on Au⁰ sites, was present due to CO adsorbed on cationic gold clusters. This highly stable species is relevant for hydrogen gas upgrade by removing CO from reformate-type gases at low temperatures. In addition, a broad absorption band in the 2000–2100 cm⁻¹ range was observed after reduction in hydrogen, due to structural and electronic changes of gold. Interestingly, the reduced gold species in ceria can be reoxidized at mild conditions. Light-off of the CO oxidation reaction took place below room temperature on the metallic gold-containing ceria but was delayed until 310 K on the ionic gold-containing sample. TPR and XPS analysis of the fresh and used catalysts corroborated the stability of ionic gold in ceria up to 393 K in the reaction gas mixture.     

Syndiospecific polymerization of propene under different processes with different bridged [(RPh)2C(Cp)(2,7-BuFlu)]ZrCl2 metallocene catalysts

The synthesis of syndiotactic polypropene was achieved by using new C_S-symmetric ansa-metallocene catalysts of the type [Ph′₂C(Cp)(2,7-^tertBu₂Flu)]ZrCl₂ (Ph′₂=Ph₂, (4-MePh)₂, 3,4′-Me₂Ph₂, (4-OCH₃Ph)₂). Applying these catalysts, the influence of the substitution pattern of the bridge on the polymerization performance can be studied and highly syndiotactic polypropene (rrrr>99%) with high molar masses and high melting temperatures (up to 153 °C) was obtained.Propene was polymerized at different temperatures under four sets of conditions: in toluene solution, bulk, toluene slurry, and gas phase with NaCl as stirred bed material. Methylaluminoxane (MAO) and methylaluminoxane supported on silicagel (MAO/SiO₂) were used as cocatalyst, respectively. In order to estimate the influence of the process on the single site properties of the catalysts, comparisons were made between polymer properties, i.e. microstructure, melting temperature, molar mass, and polymer morphology, thus allowing the effect of the support on the catalyst to be observed.