Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata, Yamagata 990-8560, Japan.
Graduate School of Science and Technology, Niigata University, 8050 Ikarashi, 2-no-cho, Nishi-ku, Niigata City 950-2181, Japan.
J Phys Chem B. 2020 Nov 19;124(46):10456-10464. doi: 10.1021/acs.jpcb.0c08021. Epub 2020 Nov 8.
Neutron diffraction measurements on Li/Li isotopically substituted 10 and 33 mol % *LiTFSA (lithium bis(trifluoromethylsulfonyl)amide)-AN- (acetonitrile-) and 10 and 33 mol % *LiTFSA-DMF-(-dimethylformamide-) solutions have been carried out in order to obtain structural insights on the first solvation shell of Li in highly concentrated organic solutions. Structural parameters concerning the local structure around Li have been determined from the least squares fitting analysis of the first-order difference function derived from the difference between carefully normalized scattering cross sections observed for Li-enriched and natural abundance solutions. In 10 mol % LiTFSA-AN- solution, 3.25 ± 0.04 AN molecules are coordinated to Li with a intermolecular Li···N(AN) distance of 2.051 ± 0.007 Å. It has been revealed that 1.67 ± 0.07 AN molecules and 2.00 ± 0.01 TFSA are involved in the first solvation shell of Li in the 33 mol % LiTFSA-AN solution. The nearest neighbor Li···N and Li···O distances are obtained to be (Li···N) = 2.09 ± 0.01 Å and (Li···O) = 1.88 ± 0.01 Å, respectively. The first solvation shell of Li in the 10 mol % LiTFSA-DMF- solutions contains 3.4 ± 0.1 DMF molecules with an intermolecular Li···O distance of 1.95 ± 0.02 Å. In highly concentrated 33 mol % LiTFSA-DMF- solutions, there are 1.3 ± 0.2 DMF molecules and 3.2 ± 0.2 TFSA in the first solvation shell of Li with intermolecular distances of (Li···O) = 1.90 ± 0.02 Å and (Li···O) = 2.01 ± 0.01 Å, respectively. The Li···TFSA contact ion pair stably exists in highly concentrated 33 mol % LiTFSA-AN and -DMF solutions.
已对 Li/Li 同位素取代的 10 和 33 mol% *LiTFSA（双（三氟甲基磺酰基）酰胺）-AN-（乙腈）和 10 和 33 mol% *LiTFSA-DMF-（-二甲基甲酰胺-）溶液进行了中子衍射测量，以便在高浓度有机溶液中获得有关 Li 第一溶剂化壳结构的见解。从仔细归一化的散射横截面观察到的富集 Li 和天然丰度溶液之间的差异导出的一阶差分函数的最小二乘拟合分析中，确定了与 Li 周围局部结构有关的结构参数。在 10 mol% LiTFSA-AN 溶液中，有 3.25 ± 0.04 个 AN 分子与 Li 配位，分子间 Li···N(AN)距离为 2.051 ± 0.007 Å。结果表明，在 33 mol% LiTFSA-AN 溶液中，1.67 ± 0.07 个 AN 分子和 2.00 ± 0.01 个 TFSA 参与了 Li 的第一溶剂化壳。获得最近邻 Li···N 和 Li···O 距离分别为 (Li···N) = 2.09 ± 0.01 Å 和 (Li···O) = 1.88 ± 0.01 Å。Li 在 10 mol% LiTFSA-DMF-溶液中的第一溶剂化壳含有 3.4 ± 0.1 DMF 分子，分子间 Li···O 距离为 1.95 ± 0.02 Å。在高浓度的 33 mol% LiTFSA-DMF-溶液中，Li 的第一溶剂化壳中存在 1.3 ± 0.2 DMF 分子和 3.2 ± 0.2 TFSA，分子间距离分别为 (Li···O) = 1.90 ± 0.02 Å 和 (Li···O) = 2.01 ± 0.01 Å。Li···TFSA 接触离子对在高浓度的 33 mol% LiTFSA-AN 和 -DMF 溶液中稳定存在。
