Two tetranuclear lanthanide complexes respectively featuring magnetocaloric effect and slow magnetization relaxation†

Two parallelogram-shape tetranuclear rare earth compounds, having the molecular formula {[Ln4(L)2(acac)4(Hthma)2]·2CH3OH·4CH3CN} (Ln = Gd (1), Dy (2); H2L = N'-(2‑hydroxy-5-methylbenzylidene)-6-(hydroxymethyl) picolinohydrazide, acac = acetylacetone, H3thma = 1,1,1-tris(hydroxymethyl)methylamine), were constructed and structurally characterized. The [Ln4O8] core of compounds 1 and 2 are connected collectively by means of two µ2 carbonyl O atoms derived from L2− main ligands, two μ3 as well as two μ2 hydroxyl O atoms originated from two Hthma2− and two µ2 O atoms from two acac−. Magnetic research concluded that 1 displays magnetocaloric effect (−ΔSm = 29.91 J K−1 kg−1) and 2 displays extremely weak antiferromagnetic interaction among neighboring rare earth ions. Single molecule magnet behaviors were possibly detected in 2, however no characteristic maximum was reached above 2 K.