Cu(ii)–Dy(iii) and Co(iii)–Dy(iii) based single molecule magnets with multiple slow magnetic relaxation processes in the Cu(ii)–Dy(iii) complex

Abstract

Two dinuclear Schiff-base complexes [Cu^IIDy^III] and [Co^IIIDy^III] have been synthesized and structurally characterized. The AC susceptibility measurements taken at B_DC = 0.2 T show a slow magnetic relaxation typical for single-molecule magnets. Unusual is the presence of three relaxation branches in [Cu^IIDy^III]; the slowest (low-frequency) process possesses the barrier to spin reversal of U/k_B = 2.8 K and an extrapolated relaxation time as slow as τ₀ = 0.11 s. The intermediate-frequency process is typical for SMM of this class with U/k_B = 122 K and τ₀ = 9.9 × 10⁻⁷ s; an onset of the high-frequency process is evidenced and this is the fastest. In contrast, the [Co^IIIDy^III] complex free of exchange coupling exhibits only a single relaxation path with SMM parameters U/k_B = 113 K and τ₀ = 7.0 × 10⁻⁹ s.