Graduate School of Energy Science, Kyoto University, Yoshida, Kyoto 606-8501, Japan.
Phys Chem Chem Phys. 2011 Jul 21;13(27):12536-44. doi: 10.1039/c1cp20285e. Epub 2011 Jun 10.
Fluorohydrogenate salts of quaternary phosphonium cations with alkyl and methoxy groups (tetraethylphosphonium (P(2222)(+)), triethyl-n-pentylphosphonium (P(2225)(+)), triethyl-n-octylphosphonium (P(2228)(+)), and triethylmethoxymethylphosphonium (P(222(101))(+))) have been synthesized by the metatheses of anhydrous hydrogen fluoride and the corresponding phosphonium bromide or chloride precursors. The three salts with asymmetric cations, P(222m)(FH)(2.1)F (m = 5, 8, and 101), are room temperature ionic liquids (ILs) and are characterized by differential scanning calorimetry, density, viscosity, and conductivity measurements. Linear sweep voltammetry using a glassy carbon working electrode shows these phosphonium fluorohydrogenate ILs have wide electrochemical windows (>4.9 V) with the lowest viscosity and highest conductivity in the known phosphonium-based ILs. Thermogravimetry shows their thermal stabilities are also improved compared to previously reported alkylammonium cation-based fluorohydrogenate salts. Differential scanning calorimetry and X-ray diffraction revealed that tetraethylphosphonium fluorohydrogenate salt, P(2222)(FH)(2)F, exhibits two plastic crystal phases. The high temperature phase has a hexagonal lattice, which is the first example of a plastic crystal phase with an inverse nickel arsenide-type structure, and the low-temperature phase has an orthorhombic lattice. The high-temperature plastic crystal phase exhibits a conductivity of 5 mS cm(-1) at 50 °C, which is the highest value for the neat plastic crystals.
具有烷基和甲氧基基团的季鏻阳离子的氟氢酸盐（四乙基鏻（P(2222)(+))、三乙基-n-戊基鏻（P(2225)(+))、三乙基-n-辛基鏻（P(2228)(+))和三乙氧基甲甲基鏻（P(222(101))(+))) 通过无水氟化氢与相应的鏻溴化物或氯化物前体的复分解反应合成。三种具有不对称阳离子的盐，P(222m)(FH)(2.1)F（m = 5、8 和 101），是室温离子液体（ILs），并通过差示扫描量热法、密度、粘度和电导率测量进行了表征。使用玻璃碳工作电极的线性扫描伏安法表明，这些磷氟氢盐 ILs 具有>4.9 V 的宽电化学窗口，在已知的磷基 ILs 中具有最低的粘度和最高的电导率。热重分析表明，与之前报道的基于烷基铵阳离子的氟氢盐相比，它们的热稳定性也得到了提高。差示扫描量热法和 X 射线衍射表明，四乙基鏻氟氢盐 P(2222)(FH)(2)F 表现出两种塑性晶体相。高温相具有六方晶格，这是首例具有反镍砷型结构的塑性晶体相，低温相具有正交晶格。高温塑性晶体相在 50°C 时表现出 5 mS cm(-1)的电导率，这是纯塑性晶体的最高值。
