Florek-Wojciechowska M, Jakubas R, Kruk D
Department of Physics and Biophysics, University of Warmia & Mazury in Olsztyn, Oczapowskiego 4, 10-719 Olsztyn, Poland.
Phys Chem Chem Phys. 2017 May 10;19(18):11197-11205. doi: 10.1039/c7cp00788d.
H spin-lattice relaxation experiments have been performed for [NH(CH)]SbCl (tris(dimethylammonium)nonachlorodiantimonate(iii)) in the temperature range of 253-313 K and a broad range of frequencies - from 4 kHz to 40 MHz. From the analysis of quadrupolar relaxation enhancement effects (quadrupolar peaks) associated with N nuclei, two lattice sites characterized by different electric field gradient tensors have been revealed. The N quadrupolar couplings and asymmetry parameters at these sites differ by a factor of about two. Three motional processes have been identified and attributed to the overall dynamics of the NH(CH) cations (slow motion), dynamics of the NH groups (intermediate motion) and methyl group rotation (fast motion). It has been shown that the slow dynamics is only weakly temperature dependent, while the intermediate and fast motional processes are characterized by activation energies of 2.92 kJ mol and 0.41 kJ mol, respectively. The correlation time of the slow dynamics is of the order of μs, while the intermediate dynamics is faster by 2-3 orders of magnitude (depending on temperature). All correlation times have turned out to be independent of the position of the cations in the lattice (they are the same for both lattice sites). The analysis presented in this work is an example of the potential of the quadrupolar relaxation enhancement effects as a method revealing information on the dynamics and structure of solids.
已对[NH(CH)]SbCl（三（二甲基铵）九氯二锑酸（III））在253 - 313 K的温度范围以及4 kHz至40 MHz的宽频率范围内进行了H自旋 - 晶格弛豫实验。通过对与N核相关的四极弛豫增强效应（四极峰）的分析，揭示了两个具有不同电场梯度张量特征的晶格位置。这些位置的N四极耦合和不对称参数相差约两倍。已识别出三种运动过程，并将其归因于NH(CH)阳离子的整体动力学（慢运动）、NH基团的动力学（中间运动）和甲基旋转（快运动）。结果表明，慢动力学仅对温度有微弱依赖性，而中间和快运动过程的活化能分别为2.92 kJ/mol和0.41 kJ/mol。慢动力学的相关时间约为微秒量级，而中间动力学快2 - 3个数量级（取决于温度）。所有相关时间均与阳离子在晶格中的位置无关（两个晶格位置的相关时间相同）。本文所呈现的分析是四极弛豫增强效应作为一种揭示固体动力学和结构信息方法的潜力的一个例子。
