Detailed magnetic properties and theoretical calculation in ferromagnetic coupling DyIII-MII 3d-4f complexes based on a 1,4,7,10‑tetraazacyclododecane derivative

The magnetic properties of five Dy III -M II 3d-4f complexes (M = Mn, Fe, Co, Ni and Zn) were studied in detail by comparison due to the same molecule construction. The Dy III -M II assemble (M = Mn, Fe and Ni) behave as field-induced SMMs resulting from the ferromagnetic coupling between Dy III and M II ions, while Dy III -Zn II is SIM and Dy III -Co II does not show the magnetic relaxation. • In this paper, a series of Dy III -M II 3d-4f complexes (M = Mn, Fe, Co, Ni and Zn) were synthesized. • Their molecules are isostructure so the magnetic properties can be compared for understanding the magnetostructural correlation. • When M = Mn, Fe and Ni, the complexes exhibit ferromagnetic coupling between Dy III and M II ions, and behave as field-induced SMMs. However, antiferromagnetic Dy III -Co II complex does not cause relaxation of magnetization. Four Dy-based 3d-4f complexes [M II Dy III (H 2 L)(NO 3 ) 3 ](CH 3 OH) 2 (H 4 L = N , N' , N'' , N''' -tetra(2-hydroxy-3-methoxy-5-methylbenzyl)-1,4,7,10-tetraazacyclododecane, M = Mn ( 2 ), Fe ( 3 ), Co ( 4 ) and Ni ( 5 ), the solvent of compound 5 is uncertain) were synthesized through the reference method of complex [Zn II Ln III (H 2 L)(NO 3 ) 3 ](CH 3 OH) 2 (1) . The magnetic properties of all the five complexes were measured for comparison. The magnetic results show that all the complexes except 4 behave as single-molecule magnets (SMMs). A magnetostructural analysis and theoretical calculation indicate the ferromagnetic coupling in 2 , 3 and 5 as well as the antiferromagnetic coupling in 4 between Dy III and transition metal ions, while the SMM properties of 1 are caused by the anisotropy of single Dy III ions only. Unexpectedly, neither of the magnetic anisotropic ions in one molecule, namely Dy III and Co II , provides greater advantages for SMM performance. This investigation experimentally proves that the coexistence of magnetic anisotropy of lanthanide ions and ferromagnetic coupling between lanthanide and transition metal ions is important for the design of 3d-4f SMMs.