Tuning the ligand field in seven-coordinate Dy(III) complexes to perturb single-ion magnet behavior

Two mononuclear seven-coordinate Dy(III) complexes [Dy(TPA)Cl3] (1) and [Dy(TPA)(OPhCl2NO2)3]·0.5CH2Cl2 (2) have been synthesized based on the neutral ligand tris[(2-pyridyl)methyl]amine (TPA) and either the strong strength ligand 2,6-dichloro-4-nitrophenol (Cl2NO2PhOH) or the weak ligand field donor Cl−. The Dy(III) centers in compexes 1 and 2 have seven-coordinated capped octahedral and capped trigonal prismatic coordination geometries, respectively. Magnetic investigations showed that both complexes display field-induced slow magnetic relaxation. The energy barrier for 2 is higher than that of 1, which is due to the strong ligand field of Cl2NO2PhO−versus Cl−, leading to a larger magnetic anisotropy of 2 as compared to 1.