Synthesis, structures and magnetic properties of dysprosium(III) complexes based on amino-bis(benzotriazole phenolate) and nitrophenolates: influence over the slow relaxation of the magnetization.

We report the synthesis and crystal structures of four dysprosium(III) complexes based on the amino-bis(benzotriazole phenolate) ligand (C1NNBiBTP-H2). Whereas a pentagonal bipyramid complex [Dy(C1NNBiBTP-H)Cl2DMF]•THF (1•THF) is obtained in the absence of co-ligands, the association with nitrophenolate derivatives bearing distinct number and position of nitro groups, affords a series of octacoordinated complexes of formulas [Dy(C1NNBiBTP)L1(MeOH)2] (2), [Dy(C1NNBiBTP)L2(MeOH)2] (3) and [Dy(C1NNBiBTP)L3(MeOH)2] (4) (HL1 = 2,4-Dinitrophenol; HL2 = 2,4,6-Trinitrophenol ; HL3 = 2,5-Dinitrophenol). Investigations of the magnetic properties reveal that all the complexes exhibit a field-induced slow relaxation of the magnetization, mainly driven by a Raman relaxation. The observed distinct dynamics could be ascribed to the substituents’ influence of the nitrophenolate that affects the Dy-O(phenoxide) distance.