A seven-coordinated DyIII single-ion magnet with C2v symmetry constructed by a multidentate Schiff-base ligand

Abstract

Two isostructural mononuclear lanthanide complexes [Ln(H₂L)Cl₃](Ln = Dy(1), Tb(2), H₂L = 6,6′-(((oxybis(2,1-phenylene))bis-(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol)) were synthesized by solvothermal reaction. In both complexes, the Ln^III ions are seven-coordinated with a LnO₄Cl₃ coordination core in the C_2v symmetry. Magnetic measurements reveal that Dy^III complex 1 shows field-induced two-step magnetization relaxation processes with U_eff = 53.47 K (slow relaxation) and 26.94 K (fast relaxation), respectively. The analysis of energy levels and eigenstates suggests that the mixed ground state doublets result in the field induced single-ion magnet behaviour of complex 1. In addition, the magneto-structural correlation, including the easy magnetic axis of Dy^III ion, was further discussed based on an electrostatic model calculation. This work gave another example of designing low-coordinated Ln-SIMs by utilizing a multidentate Schiff-base ligand with large steric hindrance.