Nanoporosity and exceptional negative thermal expansion in single-network cadmium cyanide
Nanoporosity and exceptional negative thermal expansion in single-network cadmium cyanide
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DOI：
10.1002/anie.200704421
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Kepert, Cameron J.
中科院分区：
文献类型：
--
作者：
Phillips, Anthony E.;Goodwin, Andrew L.;Kepert, Cameron J.
在面心立方空间群MFD3中对Cd(CN)2·CCl4的结构进行了解析和精化。~(113)Cd-核磁共振研究表明，在双网络Cd(CN)2中，氰化桥几乎在统计上是无序的；[1]在本工作中，这个空间群中的滑动面将氰化物的C位和N位相互映射。CCl4客体的氯原子围绕三重轴线无序排列，由三个等值位置分别模拟。本研究中使用的样品在375K氮气低温下解溶2~24小时，直到晶胞参数随时间变得稳定。然后收集了冷却时的热膨胀数据：在375至100K之间进行了可变温度运行，并在选定温度下进行了完整的结构确定。全结构测定(参见图2)用于描述完全去溶阶段的S1)通过在间隔0.6的360帧中收集Ewald球体的象限上的强度数据来执行。曝光时间从10到20 S不等，具体取决于晶体的大小和衍射性质。通过原位收集通常包含3×20或3×25帧的矩阵来执行可变温度运行；分配给每组单胞参数的温度是在相关矩阵的中点记录的温度。
The structure of Cd (CN) 2· CCl4 was solved and refined in the face-centered cubic space group mFd 3. It has been shown by 113Cd-NMR that in double-network Cd (CN) 2 the cyanide bridges are almost statistically disordered;[1] this same disorder is modeled in the present work by a glide plane in this space group which maps the cyanide C and N sites onto one another. The Cl atoms of the CCl4 guests are disordered about the threefold axes, modeled by three equivalent sites each of occupancy?.The samples used in this study were left to desolvate at 375 K under a nitrogen cryostream for periods of time ranging from 2 to 24 h, until the unit cell parameter became stable with time. Thermal expansion data were then collected on cooling: both variable temperature runs between 375 and 100 K and full structural determinations at selected temperatures were performed. Full structure determinations (see Fig. S1 for a depiction of the fully desolvated phase) were performed by collecting intensity data over a quadrant of the Ewald sphere in 360 frames spaced by intervals of 0.6. The exposure time ranged from 10 to 20 s depending on the size and diffraction properties of the crystal. Variable temperature runs were performed by in situ collection of matrices typically containing 3× 20 or 3× 25 frames; the temperature assigned to each set of unit cell parameters was that recorded at the midpoint of the relevant matrix.