Shao Dong, Zhou Yan, Pi Qian, Shen Fu-Xing, Yang Si-Run, Zhang Shao-Liang, Wang Xin-Yi
State Key Laboratory of Coordination Chemistry, Collaborative Innovation Center of Advanced Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China.
Dalton Trans. 2017 Jul 18;46(28):9088-9096. doi: 10.1039/c7dt01893b.
We herein report the syntheses, structures, and magnetic properties of two isostructural two-dimensional (2D) coordination polymers based on a pentagonal bipyramidal Co unit [Co(TODA)] and two hexacyanometallates, namely [M(CN)][Co(TODA)]·9HO (M = Cr (1), Co (2), TODA = 1,4,10-trioxa-7,13-diazacyclopentadecane). Structure analyses show that both complexes have 2D honeycomb structures where the [Co(TODA)] units are bridged by the [M(CN)] groups through three cyano groups in the facial positions. Magnetic investigation reveals ferromagnetic coupling between the Cr and Co centres through cyanides in 1. Due to the antiferromagnetic interaction between the layers, compound 1 exhibits an antiferromagnetic ordering below 11.4 K, and shows a metamagnetic phase transition under an external dc field. Due to the disorder of the TODA ligands, compound 1 shows a spin glass behavior, which leads to slow magnetic relaxation in 1. A butterfly-shaped hysteresis loop at 1.8 K can be observed with a coercive field of 720 Oe, which is quite large for cyano-bridged Cr-Co molecular magnets. For compound 2 containing the diamagnetic [Co(CN)] unit, field-induced slow magnetic relaxation was also verified, which makes compound 2 a rare example of an SIM assembled in a 2D network. An easy-plane magnetic anisotropy with a positive D value (29.9 cm by PHI and 26.5 cm by Anisofit2.0) was deduced for hepta-coordinated Co centers. These results show the efficiency of the strategy of combining cyanometallates and pentagonal bipyramidal precursors for novel molecular magnetic materials.
我们在此报告了基于五角双锥钴单元[Co(TODA)]和两种六氰基金属酸盐的两种同构二维（2D）配位聚合物的合成、结构和磁性，即[M(CN)][Co(TODA)]·9H₂O（M = Cr (1)，Co (2)，TODA = 1,4,10 - 三氧杂 - 7,13 - 二氮杂环十五烷）。结构分析表明，两种配合物均具有二维蜂窝结构，其中[Co(TODA)]单元通过[M(CN)]基团在面式位置的三个氰基桥连。磁性研究揭示了1中Cr和Co中心通过氰化物之间的铁磁耦合。由于层间的反铁磁相互作用，化合物1在11.4 K以下表现出反铁磁有序，并在外部直流场下显示出变磁相变。由于TODA配体的无序性，化合物1表现出自旋玻璃行为，这导致1中的磁弛豫缓慢。在1.8 K时可观察到具有720 Oe矫顽场的蝶形磁滞回线，这对于氰基桥连的Cr - Co分子磁体来说相当大。对于含有抗磁性[Co(CN)]单元的化合物2，也证实了场诱导的慢磁弛豫，这使得化合物2成为二维网络中组装的单离子磁体（SIM）的罕见例子。对于七配位的Co中心，推导出具有正D值（通过PHI为29.9 cm，通过Anisofit2.0为26.5 cm）的易平面磁各向异性。这些结果表明了将六氰基金属酸盐和五角双锥前体相结合的策略对于新型分子磁性材料的有效性。
