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In order to shed light upon the nature and mechanism of 4f-3d magnetic exchange interactions, a series of binuclear complexes of lanthanide(3+) and chromium(3+) with the general formula [Ln(L)5(H2O)2Cr(CN)6]·mL· nH2O (Ln=La (1), Ce (2), Pr (3), Nd (4); x=5, y=2, m=1 or 2, n=2 or 2.5; L=2-pyrrolidinone) and [Ln(L)4(H2O)3Cr(CN)6] ·nH2O (Ln=Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Er (10); x=4, y=3, m=0, n= 1.5 or 2.0; L=2-pyrrolidinone) were prepared and the X-ray crystal structures of complexes 2, 6 and 7 were determined. All the compounds consist of a Ln-CN-Cr unit, in which Ln^3+ in a square antiprism environment is bridged to an octahedral coordinated Cr^3+ ion through a cyano group. The magnetic properties of the complexes 3 and 6-10 show an overall antiferromagnetic behavior. The fitting to the experimental magnetic susceptibilities of 7 give g= 1.98, J=0.40 cm^-1, zJ'= -0.21 cm^-1 on the basis of a binuclear spin system (Scd=7/2, Scr=3/2), revealing an intra-molecular Gd^3+-Cr^3+ ferromagnetic interaction and an inter-molecular antiferromagnetic interaction. For 7 the calculation of quantum chemical density functional theory (DFT), combined with the broken symmetry approach, showed that the calculated spin coupling constant was 20.3 cm^-1, supporting the observation of weak ferromagnetic intra-molecular interaction in 7. The spin density distributions of 7 in both the high spin ground state and the broken symmetry state were obtained, and the spin coupling mechanism between Gd^3+ and Cr^3+ was discussed. 相似文献
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建立了分离分析呋喃西林及其制备杂质5-硝基糠醛二乙酯的胶束电动毛细管电泳法。考察了缓冲液的种类、浓度和p H,十二烷基硫酸钠(SDS)的浓度以及分离电压等因素对分离结果的影响。在20 mmol/L SDS-10 mmol/L Na H2PO4(p H 7.0)、分离电压15 k V的优化条件下,在10 min内即可实现分离分析。呋喃西林在5~3000μg/m L范围内、5-硝基糠醛二乙酯在2~40μg/m L范围内均呈现良好的线性关系,相关系数(r2)均大于0.9977,呋喃西林和5-硝基糠醛二乙酯的定量限分别为5μg/m L和2μg/m L,回收率为96.0%~100.2%,相对标准偏差为0.94%~3.7%。方法已应用于实际样品的分析。 相似文献
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