Molecular dynamics and phase transitions in paramagnetic [Mn(H2O)6][SiF6] investigated by 2H NMR
Molecular dynamics and phase transitions in paramagnetic [Mn(H2O)6][SiF6] investigated by 2H NMR
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通过 2H NMR 研究顺磁性 [Mn(H2O)6][SiF6] 的分子动力学和相变
DOI：
10.1016/j.jpcs.2005.02.007
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
M. Suhara
中科院分区：
文献类型：
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作者：
T. Iijima;Keigo Hamada;M. Mizuno;K. Endo;M. Suhara
测量了顺磁性[Mn（H_2O）_6][SiF_6]的~ 2 HNMR谱和自旋-晶格弛豫时间T_1随温度的变化。通过考虑四极相互作用和顺磁位移对2 H NMR谱进行了模拟。在第三阶段测量的光谱的变化被解释为水分子的180°翻转。得到了H2O 180°翻转的活化能Ea和无限温度下的跳跃速率k 0分别为35 kJmol-1和4× 1014 s-1。相I和相II的光谱变化归因于[Mn（H2O）6]2+围绕C3轴的重新取向，其中Ea和k 0值分别估计为45 kJmol − 1和1× 1013 s −1。根据几乎与温度无关的短T1值，得到电子自旋触发器的关联时间τe和交换耦合常数J分别为3.0×10− 10 s和2.9×10−3cm−1。[Mn（H2O）6]2+离子围绕C3轴的跳跃运动可引起II-III相转变。
The temperature dependences of2H NMR spectra and spin-lattice relaxation time T1have been measured for paramagnetic [Mn(H2O)6][SiF6]. The obtained2H NMR spectra were simulated by considering the quadrupole interaction and paramagnetic shift. The variation of the spectra measured in phase III was explained by the 180° flip of water molecules. The activation energy Eaand the jumping rate at infinite temperature k0for the 180° flip of H2O were obtained as 35kJmol−1and 4×1014s−1, respectively. The spectral change in phases I and II was ascribed to the reorientation of [Mn(H2O)6]2+around the C3axis where the Eaand k0values were estimated as 45kJmol−1and 1×1013s−1, respectively. From the almost temperature independent and short T1value, the correlation time for electron-spin flip-flops, τe, and the exchange coupling constant J were obtained as 3.0×10−10s and 2.9×10−3cm−1, respectively. The II–III phase transition can be caused by the onset of the jumping motion of [Mn(H2O)6]2+around the C3axis.