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RESEARCH PRODUCT

Slow relaxation in doped coordination polymers and dimers based on lanthanoids and anilato ligands

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Abstract In this work we report the synthesis, structure and magnetic properties of two lanthanoid based coordination polymers (CP) and two dimers prepared with two derivatives of the 2,5-dihydroxy-1,4-benzoquinone (C6O4X2)2− as ligands. Using the bromanilato ligand: (C6O4Br2)2− we have prepared the CP [Eu1.96Dy0.04(C6O4Br2)3(DMSO)6]·2DMSO (1) (DMSO = dimethylsulfoxide) and with the chlorocyananilato ligand: (C6O4(CN)Cl)2−) we have prepared one CP formulated as [Eu1.96Dy0.04(C6O4(CN)Cl)3(DMSO)6] (2) and two isostructural dimers: [Eu1.96Dy0.04(C6O4(CN)Cl)3(H2O)10]·6H2O (3) and [Eu2(C6O4(CN)Cl)3(H2O)10]·6H2O (4). Compounds 1, 2 and 3 are Eu(III) compounds doped with 2.0 % of Dy(III), whereas compound 4 is a pure phase of Eu(III). The X-ray structure of these CPs shows that compounds 1 and 2 present neutral (6,3)-2D networks with rectangular cavities in 1 and very distorted hexagonal cavities in 2, while 3 and 4 are isostructural and present a dimeric structure where the Ln(III) ions are connected by a bis-bidentate chlorocyananilato ligand. Each metal completes its nonacoordination environment with a terminal bidentate chlorocyananilato ligand and five water molecules in a slightly distorted capped square antiprismatic geometry. In addition, these coordination complexes have very interesting magnetic properties. Compounds 1 and 3 behave as single-molecule magnets (SMM) with energy barriers of 40.9 and 25.3 K, respectively. In contrast, compound 2 does not present any SMM behaviour.