Porous hybrid materials (Material Open-Frameworks MOFs) give rise to numerous applications in gas or solvents storage, catalysis, drug delivery [1-4]... The design of their crystal structures is based on the concept of building units, in which metals and organic ligands are joined according to the most foreseeable connections. In that way, the planar ligand squarate, C₄O₄^2-, possesses various connexion modes allowing the formation of 2D and 3D frameworks [5,6]. We particularly focused our studies on scandium compounds, because of the duality rare earth – 3d⁰ transition metal. Two isostructural hybrid materials, (A)_0.5Sc(C₄O₄)₂.xH₂O [A = C₄H₁₂N₂ (I) and C₂H₁₀N₂ (II)], have been prepared as powdered samples by slow precipitation at room temperature. Their crystal structures have been determined ab initio from X-ray powder diffraction data and solid state CPMAS NMR. Comp. I: a = 12.1080(6) Å, b = 8.2806(3) Å, c = 6.9139(3) Å, a = 91.419(3) °, b = 90.814(3) °, g = 95.489(3) °, V = 689.72(5) ų, Z = 2, S.G. P-1. The crystal structure of both hybrids, is constituted of anionic layers of scandium squarates in between which protonated amines and water molecules are intercalated. Nevertheless, examination of difference Fourier maps evidences non negligible residual electronic around the amines. The analysis by solid state NMR 13C spectroscopy (CPMAS), combined to X-ray powder diffraction data, suggests that amines can adopt two different orientations around an inversion centre.

References
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1. Polymorphs and hydrates of lead squarate, Pb(C₄O₄).nH₂O (n= 0, 1, 4): a powder diffraction study
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