Oriented Synthesis of Chair-Shaped Ln3 + Ln3 Clusters and Magnetic Properties
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2-Hydroxy-3-methoxybenzaldehyde (L1), 3-amino-1,2-propanediol (L2), trimethylacetic acid (pivalate) and Ln(NO3)3·6H2O were reacted at 80 °C to obtain two hexanuclear clusters [Ln6(HL)2(μ3-OH)2(μ3-OCH3)2(C5H9O2)10(CH3OH)2]·X (Ln = Gd (1, X = 4CH3OH), Er (2)), respectively. The aldehyde group of ligand HL1 is coupled with the amino group of HL2 to obtain 2-(2,3-dihydroxpropyliminomethyl)6-methoxyphenol (H3L). The coordination mode adopted by ligand L3− is μ4-L-k8O1,O2:O2,N1,O3:O3:O3,O4. Trimethylacetic acid adopts three different coordination modes in the six-nuclear cluster. The metal center Ln1 is in the N1O8 coordination environment, and both Ln2 and Ln3 are in the O8 coordination environment. Each of the hexanuclear complex is constructed with Ln3 triangular motifs as building blocks, and the six Ln(III) ions are arranged in a chair-shaped conformation. In magnetization studies of 1 exhibited a large magnetocaloric effect of 20.0 J kg−1 K−1 at 4 K for ΔH = 5 T.
KeywordsSchiff-base ligand Chair-shaped Hexanuclear complex Magnetocaloric effect
This work was supported by the National Natural Science Foundation of China (21601038 and 51572050), Guangxi Natural Science Foundation (2016GXNSFAA380085 and 2015GXNSFDA139007).