High magnetization reversal barriers in luminescent dysprosium octahedral and pentagonal bipyramidal single-molecule magnets based on fluorinated alkoxide ligands

Abstract

We report the synthesis and structures of three luminescent dysprosium(III) complexes based on fluorinated alkoxide ligands of formulas [Dy(L¹)₂(THF)₄][BPh₄]·0.5THF (1), [Dy(L²)₂(THF)₅][BPh₄]·2.5THF (2) and [Dy(L³)₂(THF)₅][BPh₄]·2THF (3) (L¹ = (CF₃)₃CO⁻, L² = C₆F₅C₆F₄O⁻, L³ = C₆F₅C(CH₃)O⁻). Despite the different dysprosium ion geometries (octahedral vs. distorted pentagonal bipyramidal), these systems exhibit a single-molecule magnet (SMM) behavior, but with distinct relaxation dynamics. Moreover, a typical dysprosium-based luminescence is observed for the three complexes, which make them bifunctional magneto-luminescent SMMs. Remarkably, complex 3 exhibits a high anisotropy barrier of 1469 cm⁻¹ and a blocking temperature of 22 K, making it one of the most performant alkoxide-based SMMs with the highest blocking temperature for a luminescent SMM.