A series of 3d–4f heterometallic three-dimensional coordination polymers: syntheses, structures and magnetic properties

Abstract

Seven lanthanide–cobalt heterometallic three-dimensional coordination polymers: {[Ln₃Co₂(BPDC)₅(HBPDC)(H₂O)₅](ClO₄)₂·mH₂O}_n (Ln = Eu (1, m = 10.25), Gd (2, m = 8), Tb (3, m = 9.5), Dy (4, m = 11), Ho (5, m = 10.5), Tm (6, m = 11), Lu (7, m = 10.25); BPDC = 5,5′-dicarboxylate-2,2′-dipyridine anion) were structurally and magnetically characterized. Compounds 1–7 crystallize in the orthorhombic space group Pbca, featuring a 3D sandwich framework. Magnetic properties of 2–6 have been investigated by using DC (direct current) and AC (alternating current) susceptibility measurements. Among these compounds, only compound 4 displays significant frequency dependence, albeit without reaching the characteristic maxima above 2 K, implying slow magnetic relaxation behavior in 4. After the application of a DC field, good peak shapes of AC signals were obtained and the energy barrier ΔE/k_B = 62.89 K and the preexponential factor τ₀ = 6.16 × 10⁻⁸ s. To our knowledge, 4 has the highest energy barrier in Ln–Co SMM systems hitherto.