Bis-phenoxido and bis-acetato bridged heteronuclear {CoIIIDyIII} single molecule magnets with two slow relaxation branches

Abstract

Two bis-μ-phenoxido–bis-μ-acetato heterobimetallic {Co^IIIDy^III} complexes 1 and 2, formulated as [Co^IIIDy^IIIL(μ-OAc)₂(NO₃)₂] derived from the comparable hexadentate Schiff bases N,N′-ethylenebis(3-ethoxysalicylaldimine) and N,N′-ethylenebis(3-methoxysalicylaldimine) were synthesized and X-ray structure analysis confirms their nearly identical structures. These are the first examples of bis(μ-phenoxido)–bis(μ-carboxylato) {Co^IIIDy^III} systems. The AC susceptibility measurements show that both complexes exhibit a field-induced slow magnetic relaxation with two relaxation branches. While the high-frequency process spans the usual range of the relaxation time for analogous single molecule magnets (τ₀ ∼ 10⁻⁷ s), the low-frequency branch is as slow as τ ∼ 0.1 s at T = 1.9 K and B = 0.2 T.