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121.
Zhigang Xue Seok Kyun Noh Won Seok Lyoo 《Journal of polymer science. Part A, Polymer chemistry》2008,46(9):2922-2935
2‐[(Diphenylphosphino)methyl]pyridine (DPPMP) was successfully used as a bidentate ligand in the iron‐mediated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) with various initiators and solvents. The effect of the catalytic system on ATRP was studied systematically. Most of the polymerizations with DPPMP ligand were well controlled with a linear increase in the number‐average molecular weights (Mn) versus conversion and relatively low molecular weight distributions (Mw/Mn = 1.10–1.3) being observed throughout the reactions, and the measured molecular weights matched the predicted values. Initially added iron(III) bromide improved the controllability of the polymerization reactions in terms of molecular weight control. The ratio of ligand to metal influenced the controllability of ATRP system, and the optimum ratio was found to be 2:1. It was shown that ATRP of MMA with FeX2/DPPMP catalytic system (X = Cl, Br) initiated by 2‐bromopropionitrile (BPN) was controlled more effectively in toluene than in polar solvents. The rate of polymerization increased with increasing the polymerization temperature and the apparent activation energy was calculated to be 56.7 KJ mol?1. In addition, reverse ATRP of MMA was able to be successfully carried out using AIBN in toluene at 80 °C. Polymerization of styrene (St) was found to be controlled well by using the PEBr/FeBr2/DPPMP system in DMF at 110 °C. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2922–2935, 2008 相似文献
122.
The geometry, frequency, and intensity of the vibrational bands of imidazo[1,2-a]pyridine (which is abbreviated as impy) were
obtained by the density functional theory (DFT) calculations with BLYP, B3LYP, and B3PW91 functionals and 6-31G(d) basis set.
The optimized geometric bond lengths and bond angles are in good agreement with the available X-ray data. The infrared spectrum
of imidazo[1,2-a]pyridine was computed by the DFT method in order to reproduce the vibrational wavenumbers and intensities
with an accuracy, which allows reliable vibrational assignments. Total energy distribution and isotopic shifts have been calculated
in order to help for the perfect assignment of the vibrational modes. The zinc halide complexes Zn(impy)2X2 [X = Cl, Br, and I] have also been synthesized. The compounds were characterized using the elemental analysis, FT-IR spectra,
and quantum chemical calculations. The geometry optimization of Zn(impy)2X2 yields distorted tetrahedral environment around Zn ion. 相似文献
123.
M. Priya 《Physica B: Condensed Matter》2008,403(1):67-74
Pure and ZnO and CdO added (separately) polycrystals of NaCl, KCl and (NaCl)0.5(KCl)0.5 were prepared by the melt method. Density, atomic absorption spectroscopic and X-ray diffraction measurements indicate that the ZnO and CdO have entered into the lattices of alkali halide crystals. The dielectric measurements indicate that the dielectric parameters increase with the increase in temperature. Also, the dielectric constant and dielectric loss factor values decreased whereas the electrical conductivities increased with the increase in frequency of the AC applied. Significant changes have been observed with the dielectric parameters caused by ZnO and CdO additions. Also, the depth profile study was carried out on CdO added crystals which indicates that the dopant addition creates different layers along the crystal with increase of dopant content from top to bottom. 相似文献
124.
《Magnetic resonance in chemistry : MRC》2002,40(11):716-722
205Tl longitudinal relaxation rate measurements were performed on several thallium(III) complexes with the composition Tl(OH)n(H2O)6?n(3?n)+ (n = 1,2), Tl(Cl)n(H2O)m?n(3?n)+, Tl(Br)n(H2O)m?n(3?n)+ (m = 6 for n = 1–2, m = 5 for n = 3, m = 4 for n = 4), Tl(CN)n(H2O)m?n(3?n)+ (m = 6 for n = 1–2, m = 4 for n = 3–4) in aqueous solution, at different magnetic fields and temperatures. 13C and 2D isotopic labelling and 1H decoupling experiments showed that the contribution of the dipolar relaxation path is negligible. The less symmetric lower complexes (n < 4) had faster relaxation rate dominantly via chemical shift anisotropy contribution which depended on the applied magnetic field: T1 values are between 20 and 100 ms at 9.4 T and the shift anisotropy is Δσ = 1000–2000 ppm. The tetrahedral complexes, n = 4, relax slower; their T1 is longer than 1 s and the spin–rotation mechanism is probably the dominant relaxation path as showed by a temperature dependence study. In the case of the TlCl4? complex, presumably a trace amount of TlCl52? causes a large CSA contribution, 300 ppm. Since the geometry and the bond length for the complexes in solution are known from EXAFS data, it was possible to establish a correlation between the CSA parameter and the symmetry of the complexes. The relaxation behaviour of the Tl–bromo complexes is not in accordance with any known relaxation mechanism. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
125.
Vishal H. Purecha 《Tetrahedron letters》2008,49(36):5252-5254
Palladium β-diketonate complexes are reported as efficient catalysts for the selective synthesis of monosubstituted arylferrocenes by a cross-coupling reaction of bis(ferrocenyl)mercury with aryl halides. The present protocol was applicable to aryl halides providing good to excellent yields of the desired products. 相似文献
126.
A series of new S-methyl O-fluoroalkyl N-alkyl(aryl)imidothiocarbonates were prepared by S-methylation of various fluoroalkylated thiocarbamates with methyl iodide in the presence of cesium carbonate and tetrabutylammonium iodide (TBAI) in tetrahydrofuran (THF) at room temperature. As expected from the mostly soft electrophilic alkyl halide (MeI), no isomer products derived from N-methylation were detected. The products were characterized by spectroscopic (1H, 13C and 19F) NMR, infrared, and high-resolution mass spectrometric techniques. 相似文献
127.
通过稀土氯化物与席夫碱钠盐的交换反应制备了一系列以 3,5-二叔丁基水杨醛缩苯胺为配体的稀土席夫碱配合物. 对其中的钕席夫碱配合物进行了 X射线单晶衍射分析, 发现其单晶结构为五角双锥构型, 所得席夫碱稀土配合物可以单组分催化 ?-己内酯开环聚合. 深入研究了钕席夫碱配合物催化己内酯的开环聚合机理, 考察了不同聚合条件对单体转化率、产物分子量及分子量分布的影响. 结果表明, 该聚合反应速率为一级, 聚合反应具有较好的可控性. 聚合物端基分析表明, 聚合反应以配位-插入机理进行. 相似文献
128.
十二烷基磺酸根插层水滑石负载纳米钯催化的 Suzuki 偶联反应 总被引:1,自引:0,他引:1
首次制备了十二烷基硫酸根 (DS–) 插层水滑石负载的纳米钯无膦配体型的 Suzuki 偶联反应催化剂. DS–进入到水滑石层间, 使层间距从微孔增至 2.9 nm, 从而有利于中等尺度的有机分子在催化剂表面的扩散. 进一步以 PdCl42–交换该水滑石得到 DS–和 PdCl42– 双插层的水滑石. 还原后可得到层间插有金属钯纳米团簇的水滑石. 由于 DS–插层后在水滑石层板间形成的空间有限, 限制了 Pd0 团簇的进一步生长. 作为一种亲油性的非均相催化剂, 该类催化剂可有效促进卤代芳烃与苯硼酸的 Suzuki 偶联反应. 催化剂循环使用 5 次后活性基本得以保持. 相似文献
129.
采用水热法合成了不同粒径的NaLa(MoO4)2∶Eu3+微晶.通过调节乙二醇浓度和反应时间,研究了NaLa(MoO4)2∶Eu3+微晶的形貌演变过程,在水热条件下180 ℃反应16 h获得了均一梭子形NaLa(MoO4)2∶Eu3+微晶,其晶粒长度约为2.0 μm.荧光光谱分析表明,Eu3+取代了NaLa(MoO4)2中La3+的格位, Eu3+在613 nm处红光发射(5D0–7F2跃迁)的浓度猝灭机理是电偶极-电四极相互作用,并发生了Eu3+( 5D1 ) + Eu3+(7F0 )→ Eu3+( 5D0 ) + Eu3+(7F3) 交叉弛豫,由此导致浓度猝灭.
关键词:
钼酸盐
水热法
稀土离子
发光 相似文献
130.