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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >~(139)La NMR Relaxation and Chemical Shift Studies in the Aqueous Nitrate and Chloride Solutions
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~(139)La NMR Relaxation and Chemical Shift Studies in the Aqueous Nitrate and Chloride Solutions

机译：硝酸盐和氯化物水溶液中的〜（139）La NMR弛豫和化学位移研究

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~(139)La NMR relaxations and chemical shifts in the aqueous nitrate and chloride solutions at 274-343 K were studied. The solutions in this study were La(NO_3)_3-LiNO_3 or -HNO_3, and LaCl_3 or -HCl systems. The dependencies of the slope for the plot of 1/T_1(s~(-1)) vs η/T (cP K~(-1)) on the anion concentration showed that nitrate ions form inner-sphere complexes with lanthanum in a relatively low concentration but chloride ions scarcely form below about 4.3 mol/L. In the LaCl_3-LiCl systems, the quadrupole coupling constants obtained by the temperature dependencies of 1/T_1 below about 4.3 mol/L ranged from 3.1 to 3.4 MHz, which agreed well with the value of hydrated lanthanum. In the LaCl_3-HCl systems, however, the quadrupole coupling constants slightly increased with an increase in chloride ion concentration even below about 4.3 mol/L, indicating that chloride ions possibly begin to form inner-sphere complexes. Activation energies for the rotational motion of lanthanum were determined in all of the solutions by the T_1 analyses using the Arrhenius equation. The activation energies in the nitrate concentration range from 0 to 0.1 mol/L were about 14 kJ/mol and in that above 1 mol/L about 18 kJ/mol. On the basis of the quantitative analysis for the activation energies, these values were regarded as the energies for a breaking the hydrogen bond of H_2O-H_2O. While in the chloride ion systems, the activation energies gradually decreased above 0.6 mol/L, indicating that hydrated lanthanum ions are gradually removed from a net structure of the aqueous solution by being packed by chloride ions. Chemical shifts obtained from a series of experiments also showed that chloride ions do not form inner-sphere complexes with lanthanum below about 4.3 mol/L. Furthermore, the chloride ions induce downfield shifts and nitrate ions induce upfield relative to the value of hydrated lanthanum. It is likely that the downfield shifts in the chloride systems are due to the result of an overlapping closed-shell repulsion.
机译：研究了硝酸盐和氯化物水溶液在274-343 K下的〜（139）La NMR弛豫和化学位移。在这项研究中的解决方案是La（NO_3）_3-LiNO_3或-HNO_3，以及LaCl_3或-HCl系统。 1 / T_1（s〜（-1））vsη/ T（cP K〜（-1））曲线的斜率与阴离子浓度的关系表明，硝酸根离子与镧系元素形成内球络合物。相对较低的浓度，但低于约4.3 mol / L几乎不会形成氯离子。在LaCl_3-LiCl系统中，由低于约4.3 mol / L的1 / T_1的温度依赖性获得的四极耦合常数在3.1至3.4 MHz范围内，与水合镧的值非常吻合。然而，在LaCl_3-HCl系统中，四氯偶合常数随氯离子浓度的增加而略有增加，甚至低于约4.3 mol / L，这表明氯离子可能开始形成内球络合物。通过使用阿伦尼乌斯（Arrhenius）方程的T_1分析，在所有溶液中确定了镧旋转运动的活化能。在硝酸盐浓度范围从0到0.1mol / L的活化能为约14kJ / mol，而在高于1mol / L的活化能为约18kJ / mol。在对活化能的定量分析的基础上，这些值被认为是破坏H_2O-H_2O氢键的能量。在氯离子系统中，活化能在0.6 mol / L以上逐渐降低，这表明水合镧离子通过被氯离子堆积而逐渐从水溶液的净结构中去除。通过一系列实验获得的化学位移也表明，氯离子不会与镧（约低于4.3 mol / L）形成内球络合物。此外，相对于水合镧的值，氯离子引起低场迁移，硝酸根离子引起高场迁移。氯化物系统的低场偏移很可能是由于重叠的闭壳排斥力造成的。

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