Synthesis and Characterization of Prussian Blue Analogues Incorporating the Edge-Bridged Octahedral [Zr6BCl12]2+ Cluster Core

In attempts to produce a microporous magnet, two approaches were explored for expanding the Prussian blue
structure type via incorporation of edge-bridged octahedral [Zr6ZCl12]2+ (Z = B, Be) cluster cores. Dissolution of
Rb5Zr6BCl18 and K5Zr6BeCl15 in an acetonitrile solution of Et4N(CN) led to the isolation of (Et4N)5[Zr6BCl12(CN)6] (1)
and (Et4N)5[Zr6BeCl12(CN)6]·2MeCN·2THF (2), respectively. The crystal structure of 1·1.5MeCN revealed the expected
cyano-terminated cluster complex with a trans-N···N span of 11.73(3) Å. Unfortunately, both [Zr6ZCl12(CN)6]5-
clusters rapidly lose their cyanide ligands in aqueous solution making them ill-suited for solid-forming reactions
with hydrated metal ions. Such outer-ligand exchange, however, allows the use of [Zr6BCl18]4- in the synthesis of
expanded Prussian blue-type solids through reactions with [Cr(CN)6]3-. The use of 2.2 M aqueous LiCl to stabilize
the cluster during the reaction gave (Et4N)2[Zr6BCl12][Cr(CN)6]Cl·3H2O (3), while the use of 1 M acetic acid yielded
(Et4N)2[Zr6BCl12][Cr(CN)6]Cl·2H2O·CH3CO2H (4). A Rietveld refinement against X-ray powder diffraction data collected
for 3 confirmed the presence of a cubic Prussian blue framework structure, featuring alternating [Zr6BCl12]2+ cores
and [Cr(CN)6]3- anions. The temperature dependence of magnetization data obtained for 4 revealed activation of
magnetic exchange interactions between the S = 1/2 cluster units and the S = 3/2 hexacyanochromate complexes
below 10 K.

为制备微孔磁性材料，研究者们探讨了两种扩展普鲁士蓝结构类型的方法，即通过引入边缘桥连的八面体[Zr6ZCl12]2+（Z = B, Be）簇核。将Rb5Zr6BCl18和K5Zr6BeCl15溶解于乙腈溶液中的Et4N(CN)，分别得到了(Et4N)5[Zr6BCl12(CN)6]（1）和(Et4N)5[Zr6BeCl12(CN)6]·2MeCN·2THF（2）。1·1.5MeCN的晶体结构揭示了预期的氰基终止簇复合物，其跨环N···N距离为11.73(3) Å。遗憾的是，这两种[Zr6ZCl12(CN)6]5-簇在水中迅速失去氰基配体，使其不适合与水合金属离子形成固态反应。然而，这种外配体交换允许使用[Zr6BCl18]4-通过与其反应合成扩展的普鲁士蓝型固体。在反应过程中，使用2.2 M水合LiCl稳定簇得到了(Et4N)2[Zr6BCl12][Cr(CN)6]Cl·3H2O（3），而使用1 M乙酸得到了(Et4N)2[Zr6BCl12][Cr(CN)6]Cl·2H2O·CH3CO2H（4）。针对3号样品收集的X射线粉末衍射数据进行的Rietveld精炼证实了立方普鲁士蓝框架结构的存在，该结构以交替的[Zr6BCl12]2+核和[Cr(CN)6]3-阴离子为特征。4号样品在10 K以下的磁化率数据表明，S = 1/2簇单元与S = 3/2六氰铬酸复合物之间的磁交换作用被激活。