Synthesis, Structure, and Magnetic Properties of Two New Vanadocarboxylates with Three-Dimensional Hybrid Frameworks

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Abstract
(VIII(OH))2{C6H2(CO2)4}·4H2O (labeled MIL-60) and VIII(OH){2(O2C)C6H2(COOH)2}·H2O (labeled MIL-61) were hydrothermally synthesized from mixtures of VCl3, 1,2,4,5-benzenetetracarboxylic acid, and water heated for 3 days at 473 K. The structure of MIL-60 was solved from single-crystal X-ray diffraction data in the triclinic centrosymmetric P1 (No. 2) space group with lattice parameters a = 6.3758(5) Å, b = 6.8840(5) Å, c = 9.0254(5) Å, α = 69.010(2)°, β = 85.197(2)°, γ = 79.452(2)°, V = 363.53(5) Å3, and Z = 1. The structure of MIL-61 was ab initio determined from an X-ray powder diffraction pattern. MIL-61 crystallizes in the Pnma (No. 62) orthorhombic space group with lattice parameters a = 14.8860(1) Å, b = 6.9164(1) Å, c = 10.6669(2) Å, V = 1098.23(3) Å3, and Z = 4. Both structures contain the same inorganic building block that consists of trans chains of VIIIO4(OH)2 octahedra. The three-dimensional frameworks of MIL-60 and MIL-61 are constituted by the linkage of these chains via the organic molecules so delimiting the channels or cages where the water molecules are encapsulated. The magnetic behavior of these two phases is presented: MIL-60 is paramagnetic, and MIL-61 antiferromagnetically orders below TN = 55(5) K.