A comprehensive variable temperature, pressure and frequency multinuclear (1H, 2H, and 19F) magnetic resonance study was undertaken on selectively deuterated 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIM TFSA) ionic liquid isotopologues. This study builds on our earlier investigation of the effects of increasing alkyl chain length on diffusion and dynamics in imidazolium-based TFSA ionic liquids. Fast field cycling 1H T1 data revealed multiple modes of motion. Through calculation of diffusion coefficient (D) values and activation energies, the low- and high-field regimes were assigned to the translational and reorientation dynamics respectively. Variable-pressure 2H T1 measurements reveal site-dependent interactions in the cation with strengths in the order MD3 > CD3 > CD2, indicating dissimilarities in the electric field gradients along the alkyl chain, with the CD2 sites having the largest gradient. Additionally, the α saturation effect in T1 vs. P was observed for all three sites, suggesting significant reduction of the short-range rapid reorientational dynamics. This reduction was also deduced from the variable pressure 1H T1 data, which showed an approach to saturation for both the methyl and butyl group terminal methyl sites. Pressure-dependent D measurements show independent motions for both cations and anions, with the cations having greater D values over the entire pressure range.

中文翻译：

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通过变温变压 NMR 弛豫测量和扩散测量研究 BMIM TFSA 离子液体的动力学


对选择性氘化 1-丁基-3-甲基咪唑鎓双（三氟甲基磺酰基）酰胺 (BMIM TFSA) 离子液体同位素体进行了全面的变温、变压和变频多核（1H、2H 和 19F）磁共振研究。这项研究建立在我们早期对增加烷基链长度对咪唑基 TFSA 离子液体扩散和动力学影响的研究的基础上。快速场循环 1H T1 数据揭示了多种运动模式。通过计算扩散系数 (D) 值和活化能，低场和高场状态分别分配给平移和重定向动力学。变压 2H T1 测量揭示了阳离子中位点依赖性相互作用，其强度顺序为 MD3 > CD3 > CD2，表明沿烷基链的电场梯度存在差异，其中 CD2 位点具有最大梯度。此外，在所有三个位点都观察到 T1 与 P 中的 α 饱和效应，表明短程快速重定向动力学显着减少。这种减少也是从可变压力 1H T1 数据中推断出来的，该数据显示甲基和丁基末端甲基位点均接近饱和。压力相关的 D 测量显示阳离子和阴离子的独立运动，其中阳离子在整个压力范围内具有更大的 D 值。