Heterometallic Heptanuclear [Cu5Ln2] (Ln = Tb, Dy, and Ho) Single-Molecule Magnets Organized in One-Dimensional Coordination Polymeric Network

The reaction of a multisite coordination ligand, LH3, with Cu­(II) salts and Ln­(NO3)3·nH2O in a 1:2:1 stoichiometric ratio in the presence of triethylamine was found to afford a series of one-dimensional heterometallic [{Cu5Ln2(L)2(μ3–OH)4(ClO4)­(NO3)3(OH2)5}­(ClO4)2(H2O) x ]∞ [Ln = Tb­(1), Dy­(2) and Ho­(3), x = 4.25, 5.5, and 5 for 1–3, respectively] coordination polymers. Complexes 1–3 have been characterized by single crystal X-ray crystallography. The detailed study of the magnetic properties has also been performed and compared with the parent [Cu5Ln2] molecular analogues. The ac susceptibility measurements for complexes 1–3 confirm their SMM behavior with the following characteristics: Δeff/k B = 23.4 K, τ0 = 1.1 × 10–6 s and Δeff/k B = 27.9 K, τ0 = 6.6 × 10–7 s under 0 and 1200 Oe dc fields, respectively for 1; Δeff/k B = 8.3 K, τ0 = 3.1 × 10–6 s for 2 under 0 dc field. For 3, the fast QTM below 4 K prevents the estimation of the SMM energy barrier. Remarkably, the magnetic and SMM properties of the previously reported molecular [Cu5Ln2] analogues are preserved after their assembly in these coordination networks.