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首页> 外文期刊>The Journal of Chemical Physics >ALKYL CHAIN DYNAMICS IN PEROVSKITE BILAYERS AND THEIR VARIATION WITH STRUCTURAL PHASE AS STUDIED BY POWDER AND SINGLE CRYSTAL NMR
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ALKYL CHAIN DYNAMICS IN PEROVSKITE BILAYERS AND THEIR VARIATION WITH STRUCTURAL PHASE AS STUDIED BY POWDER AND SINGLE CRYSTAL NMR

机译：粉末和单晶NMR研究钙钛矿双分子链中的烷基链动力学及其与结构相的变化

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摘要

A single crystal magnetic resonance study of C4Cd, [(C4H9NH3)(2)Cd]Cl-4, specifically deuterated at a variety of positions is reported. This class of compound forms bilayered structures and C4Cd itself undergoes at least three phase transitions over the temperature range studied, 120 to 350 K. The experimental results yield a detailed picture of the variation of molecular ordering in the butyl chain with temperature and structural phase and bear substantial resemblance to H-2 NMR results reported for Lipid membranes. In the high and intermediate phases, complete order tensors are determined in the bilayer frame which are compared (unsuccessfully) with the disordered high temperature x-ray structure of the isomorphous manganese analog, C4Mn. On the time scale of 10(-5) s, the butyl chain is nearly stationary at 120 K where it is found to occupy the expected all-trans configuration which runs parallel to the bilayer normal. At temperatures between the intermediate phase and 120 K, a mosaic structure is observed in which the C-D bonds occupy for long times (>10(-3) s) a distribution of orientations. A qualitative model for the high and intermediate phases based on gauche-trans isomerization is presented. To explain the measured order tensors, we assume that (a) gauche-trans isomerization is coupled to molecular reorientation and (b) the configurations are distorted from ideal diamond lattice configurations so as to make molecular packing more compact. It is suggested that in the mosaic structure, configurations containing gauche sequences remain populated but the isomerization rate is dramatically slowed. (C) 1996 American Institute of Physics. [References: 27]
机译：报告了对C4Cd，[（C4H9NH3）（2）Cd] Cl-4，特别是氘代在多个位置进行的单晶磁共振研究。这类化合物形成双层结构，并且C4Cd本身在所研究的120至350 K的温度范围内经历至少三个相变。实验结果给出了丁基链中分子有序度随温度和结构相的变化的详细图片。与脂质膜的H-2 NMR结果基本相似。在高阶段和中间阶段，在双层框架中确定完整阶张量，将其与同构锰类似物C4Mn的无序高温X射线结构进行比较（但未成功）。在10（-5）s的时间尺度上，丁基链在120 K时几乎是静止的，在该处发现它占据了预期的全反式构型，该构型平行于双层法线。在中间相和120 K之间的温度下，观察到镶嵌结构，其中C-D键长时间（> 10（-3）s）占据取向分布。提出了基于gauche-反式异构化的高相和中间相的定性模型。为了解释测得的张量，我们假设（a）gauche-反式异构化与分子重新取向相关，并且（b）构型从理想的金刚石晶格构型变形，从而使分子堆积更加紧凑。有人提出，在镶嵌结构中，包含纱au序列的构型仍然存在，但异构化速率却大大降低。 （C）1996年美国物理研究所。 [参考：27]

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