A Spherical Capped Square Antiprismatic DyIII Complex Encapsulated Three Acylhydrazone Schiff Base Ligands Behaving Field-Induced Single-Ion Magnet Behaviour

One mononuclear Dy-III based complex, [Dy(L)(3)]center dot 0 center dot 25H(2)O (1) (HL= N'-(2-hydroxybenzoyl)pyridine-2-carbohydrazonamide) has been successfully synthesized and systematically characterized. Single-crystal X-ray diffraction reveals that 1 crystallizes in the orthorhombic system with space group P/21. The nine-coordinated Dy-III ion in 1 adopts distorted spherical capped square antiprism configuration (C-4v-CSAPR) with three tridentate coordination pockets. In addition, the alternating-current (ac) magnetic susceptibility investigations show that 1 exhibits slow magnetic relaxation behavior under an applied 1000 Oe field with effective energy barrier (U-eff) of 83.10 K. To understand the magnetic behaviour in depth, the magnetic axes and magneto-structural correlations are analyzed to reveal that the coordination of three ligands effectively enhances the axiality of the nine-coordinated mononuclear Dy-III complexes, thereby exhibiting the slow magnetic relaxation behaviour. This work provides a strategy to effectively improve the performance of single-ion magnets (SIMs) by introducing more ligands around the Dy-III ion, and regularizing the coordination configuration of the Dy-III ion towards an axial-type structure.