State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures , Nanjing University , Nanjing 210023 , China.
Institute of Information Engineering , Suqian College , Suqian , 223800 , China.
Inorg Chem. 2018 Oct 1;57(19):12143-12154. doi: 10.1021/acs.inorgchem.8b01762. Epub 2018 Sep 18.
Four pairs of enantiomeric dysprosium(III) phosphonates, namely, R- or S-Dy(pempH)(pempH)·12HO ( R-1 or S-1), R- or S-[Dy(pempH)(pempH)]Cl·2HO ( R-2 or S-2), R- or S-[Dy(pempH)(pempH)]Br·2HO ( R-3 or S-3), and R- or S-Dy(pempH)(pempH)·22HO ( R-4 or S-4) are reported, where R- or S-pempH represent R- or S-(1-phenylethyl)amino] methylphosphonic acid. All show homochiral chain structures, charge-balanced by counteranions. A comparison of the crystal morphologies of the R-isomers reveals that the overall shapes are quite similar for the four compounds, but the aspect ratio changes remarkably following the sequence: R-1 < R-2 < R-3 < R-4. The sequence is in agreement with the decreasing interchain interactions related to different counteranions, which is rationalized by molecular simulations. The counteranions also influence the intrachain structures and the local coordination environments of the Dy ions. As a result, compounds R-2 and R-3 exhibit distinct dual relaxation processes at zero dc field with the effective energy barriers for the slow- and fast-relaxation being 79.1 and 37.6 K for R-2, and 80.0 and 39.1 K for R-3, respectively. For compounds R-1 and R-4, however, slow magnetic relaxation is also observed at zero dc field but without the appearance of maxima down to 1.8 K.
报道了四对对映体镝（III）膦酸酯，即 R- 或 S-Dy(pempH)(pempH)·12H2O ( R-1 或 S-1)、R- 或 S-[Dy(pempH)(pempH)]Cl·2H2O ( R-2 或 S-2)、R- 或 S-[Dy(pempH)(pempH)]Br·2H2O ( R-3 或 S-3) 和 R- 或 S-Dy(pempH)(pempH)·22H2O ( R-4 或 S-4)，其中 R- 或 S-pempH 代表 R- 或 S-[(1- 苯基乙基)氨基]甲基膦酸。所有化合物均呈现同手性链状结构，由抗衡阴离子平衡电荷。对 R-异构体的晶体形态比较表明，四个化合物的整体形状非常相似，但随着序列的变化，纵横比变化显著：R-1 < R-2 < R-3 < R-4。该序列与不同抗衡阴离子相关的链间相互作用的减弱一致，这可以通过分子模拟来合理化。抗衡阴离子也影响链内结构和 Dy 离子的局部配位环境。结果，化合物 R-2 和 R-3 在零直流场下表现出明显的双弛豫过程，其中慢弛豫和快弛豫的有效能垒分别为 R-2 的 79.1 和 37.6 K，R-3 的 80.0 和 39.1 K。然而，对于化合物 R-1 和 R-4，即使在零直流场下也观察到缓慢的磁弛豫，但在 1.8 K 以下没有出现最大值。
