Nair Nanditha G, Blanco Mario, West William, Weise F Christoph, Greenbaum Steve, Reddy V Prakash
Department of Chemistry, Missouri University of Science and Technology, Rolla, Missouri 65409, USA.
J Phys Chem A. 2009 May 21;113(20):5918-26. doi: 10.1021/jp901952t.
Novel fluorinated boroxines, tris(2,6-difluorophenyl)boroxin (DF), tris(2,4,6-trifluorophenyl)boroxin (TF), and tris(pentafluorophenyl)boroxin (PF), have been investigated for potential applications in lithium ion batteries through fluoride anion binding, ab initio calculations, and ionic conductivity measurements. Structures of the fluorinated boroxines and boroxin-fluoride complexes have been confirmed by comparing their (19)F and (11)B NMR chemical shifts with those obtained by the DFT-GIAO method. The stoichiometry of the fluoride anion binding to these boroxines has been shown to be 1:1 using (19)F NMR and UV-vis spectroscopy. UV-vis spectroscopic studies show the coexistence of more than one complex, in addition to the 1:1 complex, for perfluorinated boroxin, PF. DFT calculations (B3LYP/6-311G**) show that the fluoride ion complex of DF prefers unsymmetrical, covalently bound structure (7) over the symmetrically bridged species (10) by 12.5 kcal/mol. Rapid equilibration of the fluoride anion among the three borons in these boroxines results in a single (19)F NMR absorption for all of the aromatic ortho- or para-fluorines at ambient temperature. The effect of these anion receptors on lithium ion conductivities was also explored for potential applications in dual ion intercalating lithium batteries.
新型氟化硼恶嗪，三（2,6 - 二氟苯基）硼恶嗪（DF）、三（2,4,6 - 三氟苯基）硼恶嗪（TF）和三（五氟苯基）硼恶嗪（PF），已通过氟阴离子结合、从头算计算和离子电导率测量，研究其在锂离子电池中的潜在应用。通过将氟化硼恶嗪和硼恶嗪 - 氟化物配合物的（19）F和（11）B核磁共振化学位移与密度泛函理论 - 广义膺势平面波（DFT - GIAO）方法得到的化学位移进行比较，证实了它们的结构。利用（19）F核磁共振和紫外 - 可见光谱表明，氟阴离子与这些硼恶嗪的化学计量比为1:1。紫外 - 可见光谱研究表明，除了1:1配合物外，全氟硼恶嗪PF还存在不止一种配合物。密度泛函理论计算（B3LYP/6 - 311G**）表明，DF的氟离子配合物更倾向于不对称的共价键合结构（7），而不是对称桥连物种（10），其能量差为12.5千卡/摩尔。在室温下，这些硼恶嗪中三个硼原子间氟阴离子的快速平衡导致所有芳环邻位或对位氟的单一（19）F核磁共振吸收。还探索了这些阴离子受体对锂离子电导率的影响，以用于双离子插层锂电池的潜在应用。
