Yoshinari Nobuto, Yamashita Satoshi, Fukuda Yosuke, Nakazawa Yasuhiro, Konno Takumi
Department of Chemistry , Graduate School of Science , Osaka University , Toyonaka , Osaka 560-0043 , Japan . Email:
Chem Sci. 2018 Oct 26;10(2):587-593. doi: 10.1039/c8sc04204g. eCollection 2019 Jan 14.
The design and creation of ionic crystals that show high mobility of ionic species in the solid state has long been a research topic of considerable attention not only due to the practical applications of these materials but also due to the correlation of such ionic species with ion-transport biological systems. In this work, we report the mobility of alkali metal ions (M = Li, Na, K) in the ionic crystals M[RhZnO (l-cysteinate)]·HO (M[]·HO). In M[]·HO, alkali metal ions are distributed in a disordered manner, together with a number of water molecules, within a rigid hydrogen-bonded framework of anionic clusters of []. The alternating current conductivities of M[]·HO in the solid state increase in the order of Li[]·HO < Na[]·HO < K[]·HO, which is opposite to the order of the naked ionic radii. The conductivities reach the superionic level of = 1.3 × 10 S cm at 300 K for a single crystal of K[]·HO. These results reflect the high mobility of hydrated alkali metal ions in the crystal lattice of M[]·HO, which is supported by solid-state NMR spectroscopy, together with ion diffusion experiments in the solid state. The high mobility leads to quick exchange of K ions in K[]·HO with Li and Na ions with retention of single crystallinity.
长期以来，设计和创制在固态下离子具有高迁移率的离子晶体一直是一个备受关注的研究课题，这不仅是因为这些材料的实际应用，还因为此类离子与离子传输生物系统之间的关联。在这项工作中，我们报道了碱金属离子（M = Li、Na、K）在离子晶体M[RhZnO( l - 半胱氨酸盐)]·H₂O（M[ ]·H₂O）中的迁移率。在M[ ]·H₂O中，碱金属离子与若干水分子一起以无序方式分布在[ ]阴离子簇的刚性氢键框架内。M[ ]·H₂O在固态下的交流电导率按Li[ ]·H₂O < Na[ ]·H₂O < K[ ]·H₂O的顺序增加，这与裸离子半径的顺序相反。对于K[ ]·H₂O单晶，在300 K时电导率达到1.3 × 10⁻³ S cm⁻¹的超离子水平。这些结果反映了水合碱金属离子在M[ ]·H₂O晶格中的高迁移率，这得到了固态核磁共振光谱以及固态离子扩散实验的支持。这种高迁移率导致K[ ]·H₂O中的K离子与Li和Na离子快速交换，同时保持单晶性。
