Weak Ligand-Field Effect from Ancillary Ligands on Enhancing Single-Ion Magnet Performance

A series of bis-pentamethylcyclopentadienyl-supported Dy complexes containing different ancillary ligands were synthesized and characterized. Magnetic studies showed that 1Dy [Cp-2*DyCl(THF)], 1Dy' [Cp-2*DyCl2K(THF)](n), 2Dy [Cp-2*DyBr(THF)], 3Dy [Cp-2*DyI(THF)] and 4Dy [Cp-2*DyTp] (Tp=hydrotris(1-pyrazolyl)borate) were single-ion magnets (SIMs). The 1D dysprosium chain 1Dy' exhibited a hysteresis at up to 5 K. Furthermore, 3Dy featured the highest energy barrier (419 cm(-1)) among the complexes. The effects of ancillary ligands on single-ion magnetic properties were studied by experimental, ab initio calculations and electrostatic analysis methods in detail. These results demonstrated that the QTM rate was strongly dependent on the ancillary ligands and that a weak equatorial ligand field could be beneficial for constructing Dy-SIMs.