Axial Ligand as a Critical Factor for High-Performance Pentagonal Bipyramidal Dy(III) Single-Ion Magnets
Ben Zhang, Xuefeng Guo, Pengfei Tan, Wei Lv, Xiaoye Bai, Yang Zhou, Aihua Yuan, Lei Chen, Dan Liu, Hui−Hui Cui, Ruosong Wang, Xue‐Tai Chen
Abstract
The choice of axial ligands is of great importance for the construction of high-performance Dy-based single-molecule magnets (SMMs). Here, combining axial ligands Ph3SiO– (anion of triphenylsilanol) and 2,6-dichloro-4-nitro-PhO– (the anion of 2,6-dichloro-4-nitrophenol) with a neutral macrocyclic ligand 2,14-dimethyl-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadeca-1(19),2,13,15,17-pentaene (L2N5) generates two new pentagonal bipyramidal Dy(III) complexes [DyIII(L2N5) (X)2](BPh4) (X = Ph3SiO–, 1; 2,6-dichloro-4-nitro-PhO–, 2) with strong axial ligand fields. Magnetic characterizations show that 1 possesses a large energy barrier above 1000 K and a magnetic hysteresis up to 9 K, whereas 2 only displays field-induced peaks of alternating-current susceptibilities without the hysteresis loop, even though 2 has a similar coordination geometry with 1. Detailed Ab initio calculations indicate an apparent difference in the axial negative charge between both complexes, which is caused by the diverse electron-donating properties of the axial ligands. The present work provides an efficient strategy to enhance the SMMs’ properties, which highlights that the electron-donating property of the axial ligands is especially important for constructing the high-performance Dy-based SMMs.