Organic acid–base salts have attracted increasing attention as a promising candidate of anhydrous proton conductors. In this study, we have successfully disclosed the relationship between proton conductivity and hydrogen-bond (H-bond) interactions in such kinds of organic salts, composed of dicarboxylic acid and imidazole. We have grown high-quality single crystals of imidazolium succinate (Im-Suc) or glutarate (Im-Glu) with two-dimensional H-bonding networks and measured the proton conductivity within and perpendicular to the networks. On the basis of the observed “intrinsic” proton conductivities without grain boundary contributions, their relationship to the crystal structure and molecular arrangement was investigated in detail. Importantly, in both materials, the proton conductivities within the H-bonding networks are almost 2 orders of magnitude higher than those perpendicular to the networks, demonstrating that the proton conduction is highly mediated by the H-bonds. In addition, a suitable combination and arrangement of acid and base molecules for realizing high proton conductivity is discussed in terms of their proton donating/accepting abilities (pK_a) and molecular motions. These results provide important insights into the effects of H-bonds on proton conductivity in this kind of anhydrous organic acid–base salts.

中文翻译：

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由无水有机单晶氢咪唑羧酸盐中的氢键模式引起的各向异性质子电导率

作为无水质子导体的有前途的候选者，有机酸碱盐已引起越来越多的关注。在这项研究中，我们成功地揭示了在由二羧酸和咪唑组成的这类有机盐中，质子传导性与氢键（氢键）相互作用之间的关系。我们已经生长出具有二维H键网络的琥珀酸咪唑鎓琥珀酸酯（Im-Suc）或谷氨酸盐（Im-Glu）的高质量单晶，并测量了网络内和垂直于网络的质子电导率。基于观察到的没有晶界贡献的“本征”质子电导率，详细研究了它们与晶体结构和分子排列的关系。重要的是，在两种材料中 H键网络中的质子电导率比垂直于网络的质子电导率高近2个数量级，表明质子传导是由H键高度介导的。另外，关于酸和碱分子的适当组合和排列，以实现高质子传导性，讨论了它们的质子给体/接受能力（pK _a）和分子运动。这些结果为这种无水有机酸碱盐中氢键对质子传导性的影响提供了重要的见识。