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621.
622.
A new lanthanumⅢ-ironⅢ complex [La(DMSO)5(H2O)](μ-CN)2[Fe(CN)4]·H2O 1 (DMSO=dimethylsulfoxide) has been prepared by a facile approach,ball-milling method,and characterized by X-ray diffraction. The crystal belongs to monoclinic,space group P21/n with a= 9.7125(3),b=21.5336(7),c=14.3804(5),β=93.242(3)o,C16H34FeLaN6O7S5,Mr=777.55,V =3002.8(2)3,Z=4,Dc=1.720 g/cm3,S=1.053,μ(MoKα)=2.278 mm–1,F(000)=1564,R= 0.0490 and wR=0.1270. The crystal structure analysis of 1 reveals a slightly distorted square-antiprism eightfold-coordinated La(Ⅲ) ion and a 1-D zigzag chain structure extending through the Fe-CN-La-NC-Fe linkages. The [La(DMSO)5(H2O)](μ-CN)2[Fe(CN)4] species are held together via hydrogen bonds to form a three-dimensional framework. 相似文献
623.
624.
Transfer of lanthanum ion across the adsorption of emulsifier OP at the water-nitrobenzene interface
The transfer of lanthanum ion facilitated by diantipyrylmathane (DAM) across the water/nitrobenzene (w/nb) interface and the adsorption of emulsifier OP at the w/nb interface has been studied by the cyclic voltammetry.The mechanism of the charge transfer reactions is discussed.It has been concluded that the transfer of rare earth metal ion (La3+) facilitated by neutral ionophore (DAM) at the w/nb interface is E mechanism and the nonionic surfactant (emulsifier OP) can participate in the charge transfer process as an ionophore,charge transfer catalyst and inhibitor. 相似文献
625.
Heat Capactites and Thermodynamic Properties of Lanthanum/Holmium Perchlorate Complexes with Glycine
Liu Bei‐Ping Tan Zhi‐Cheng Yu Hua‐Guang Sun Li‐Xian Lan Xiao‐Zheng Di You‐Ying Chen Zhen‐Gan Liu Ping 《中国化学》2003,21(4):396-399
The heat capacities of the two complexes, [La2(Gly)6(H2O)4]‐(ClO4)6 and [Ho2(Gly)4(H2O)4](ClO4)6·2H2O (Gly = glycine), were measured by adiabatic calorimetry in the temperature range from 78 to 375 K. A solid‐solid phase transition was found between 322.87 and 342.29 K for [Ho2(Gly)6(H2O)4](ClO4)6·2H2O, and the peak temperature, the enthalpy and the entropy of the transition were obtained to be 330.94 K, 11.65 kJ·mol?1 and 35.20 J· K?1·mol?1, respectively. No indication of any phase transition or thermal anomaly was observed for [La2 (Gly)6 (H2O)4 ] (ClO4)6. Thermal stabilities of the two complexes were investigated by thermogravimetry in the temperature range of 40–800°C. The possible mechanisms for the thermal decompositions were proposed according to the TG and DTG curves. 相似文献
626.
Jihong Cheng 《Journal of solid state chemistry》2005,178(1):234-244
A series of perovskites with the general formula La1−xAxCrO3−δ (A=Ca or Sr) have been synthesized in the solid solution range 0.0<x?0.3 and 0.0?δ?0.5x with a variety of heat treatments. High-temperature drop solution calorimetry in molten 2PbO·B2O3 at 1080 K was performed to determine their enthalpies of formation from oxides at room temperature. The enthalpy of oxidation involved in the reaction is roughly independent of oxygen nonstoichiometry (δ) in each series with a given dopant composition, but varies with composition (x). The values change from −620±260 to −280±80 kJ/mol O2 when x=0.1-0.3 for Ca-doped samples, and from −440±150 to −290±50 kJ/mol O2 for Sr-doped ones. This dependence of enthalpy of oxidation on composition suggests oxygen vacancies are increasingly short-range ordered in reduced samples. The higher oxidation state of chromium is stabilized by the substitution of alkaline earth ions, but with increasing doping, the enthalpy of formation of the fully oxidized sample in both Ca and Sr-doped systems becomes more endothermic. This destabilization effect is attributed to the large endothermic enthalpy of oxygen vacancy formation (395±30 kJ/mol of ) for the reaction (A=Ca or Sr) that over-rides the exothermic enthalpies of oxidation. At a given composition, Sr-doped LaCrO3 is more stable than its Ca-doped counterpart, which is consistent with basicity arguments. 相似文献
627.
作者曾系统研究[Ln(CCl_3COO)_3·dipy·H_2O]2配合物的合成和性质,并测定了[La(CCl_3COO)_3·dipy·H_2O]_2的晶体结构(待发表)。本文用量子化学INDO方法探讨镧配合物的电子结构和化学键。程序和参数见文献[1]。分子结构采用晶体结构数据。计算模型取配合物的一半,用HCOO~-代CCl_3COO~-,这样的近似对结果可能有影响,但在讨论羧基与La配位以及双聚机理时使图象更为简明清晰。分子骨架结构见图1,其中HCO_1O_5~-的一个氧 相似文献
628.
以十二磷钨杂多酸(Tungstophosphoric acid,H_3PW_(12)O_(40))为基体,分别通过普通浸渍法、溶胶凝胶法和超声浸渍法进行了La3+改性作用,合成了三种固体酸催化剂A-LaPW_(12)O_(40)、B-LaPW_(12)O_(40)/Si O2和C-LaPW_(12)O_(40)。采用X射线荧光光谱(XRF)、孔径比表面积测定、X射线粉末衍射(XRD)、透射电镜(TEM)、红外光谱(FT-IR)、热重(TG)、N2吸附-脱附、NH3程序升温脱附(NH3-TPD)、吡啶吸附红外光谱(Py-FTIR)、X射线光电子能谱(XPS)等方法对合成的催化剂进行了表征,并比较了以上催化剂在用于催化以油酸和甲醇为反应物经酯化反应合成生物柴油时的活性和稳定性。结果表明,B-LaPW_(12)O_(40)/Si O2具有最高催化活性,当甲醇与油酸的物质的量比为8∶1,催化剂用量为反应物总质量的2%,反应温度为65℃,反应1 h后,油酸的转化率即高达93%。循环使用B-LaPW_(12)O_(40)/Si O2催化剂六次后,油酸的转化率仍高达86.4%。B-LaPW_(12)O_(40)/Si O2的高催化活性和稳定性可归因于在溶胶凝胶的转化过程中,作为硅源材料的四乙氧基硅(TEOS)易在酸性条件下发生水解反应形成Si O2网络,进而Si O2网络中的硅醇键与H_3PW_(12)O_(40)中的H+发生配位作用,生成具有强静电吸附力的(≡Si-OH2+)(H2PW12O-40)络合物。随着该络合物的形成,促进了La3+在Si O2表面的吸附而堵塞了H_3PW_(12)O_(40)的孔道结构,抑制了H_3PW_(12)O_(40)颗粒在焙烧过程中进一步聚集长大。Si O2将作为载体并以干凝胶状态存在于B-LaPW_(12)O_(40)/Si O2催化剂中,由于Si O2凝胶的高比表面积而使B-LaPW_(12)O_(40)/Si O2具有了较大的比表面积,从H_3PW_(12)O_(40)的1.4 m2/g增加至31.3 m2/g。并且,通过吡啶吸附红外光谱确定B-LaPW_(12)O_(40)/Si O2为Br9nsted-Lewis酸型固体酸,由于Br9nsted酸位易与酯化反应过程中生成的水发生水合反应而失活,因而Lewis酸位的形成有助于减少催化剂的失活现象发生。Lewis酸位的出现可归因于(≡Si-OH2+)(H2PW12O-40)与吸附在其表面的具有强吸电子作用的La3+发生键合作用后生成了LaPW_(12)O_(40)/Si O2。 相似文献
629.
In the present work, lanthanum phenylphosphonate (LaPP)–based multilayered film was fabricated on the surface of flexible polyurethane (PU) foam by layer‐by‐layer self‐assembled method. The successful deposition of the coating was confirmed by scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX). Subsequently, the thermal decomposition and burning behavior of untreated and treated PU foams were investigated by thermogravimetric analysis (TGA) and cone calorimeter, respectively. The TGA results indicated that Tmax2 of treated PU foams were increased by approximately 15°C to 20°C as compared with untreated PU foam. The peak heat release rate (PHRR) and total heat release (THR) of PU‐6 (with 19.5 wt% weight gain) were 188 kW/m2 and 20.3 MJ/m2, with reductions of 70% and 15% as compared with those of untreated PU foam, respectively. Meanwhile, the smoke production of treated PU foam was suppressed after the construction of LaPP‐based coating. 相似文献
630.