| Abstract
| - The hydrothermal investigation of the quaternary system CuCl2·2H2O/methylenediphosphonic acid/NaOH/H2O leads to four compounds. Three of them present a new structuraltype; the fourth is isostructural with a cobalt compound and is already published. Varyingexperimental parameters such as the initial pH or the temperature allows isolation of eachcompound as a pure phase. The exception is Cu2(O3P-CH2-PO3) (labeled MIL-54) whichpresents a dense three-dimensional framework; the three other compounds are built up fromlayers between which water molecules and/or Na+ cations are intercalated. Both MIL-54and Na2Cu(O3P-CH2-PO3)·(H2O) are orthorhombic in the space group Pnma (nο. 62) withlattice parameters a = 13.7056(1) Å, b= 7.9953(2) Å, c = 4.9209(1) Å, and V = 539.23(2) Å3for MIL-54; in the space group P212121 (nο. 19), a = 9.0155(2) Å, b = 10.1795(2) Å, c =16.2084(3) Å, and V = 1487.50(5) Å3 for Na2Cu(O3P-CH2-PO3)·(H2O). The two other phasesare monoclinic (SG: C2/c (nο. 15)) with lattice parameters a = 19.193(1) Å, b = 8.6892(5) Å,c = 9.1904(5) Å, β = 105.858(2)°, and V = 1474.4(1) Å3, and a = 17.750(4) Å, b = 6.210(1) Å,c = 23.200(5) Å, β = 94.12(3)°, and V = 2550.7(9) Å3 for Cu3(H2O)2(O3P-CH2-PO3H)2·(H2O)(noted MIL-55) and Na3Cu5(O3P-CH2PO3Hx)4·(H2O)2 (x = 0.75) (noted MIL-56), respectively.The magnetic behavior of these solids was studied and explained from structural considerations: the three-dimensional MIL-54 and Na2Cu(O3P-CH2-PO3)·(H2O) exhibit an antiferromagnetic behavior below TN ≈ 45(2) and 50(2) K, respectively, and the other compoundsare paramagnetic. Finally, the structural evolution of the title solids depending on the pHis discussed via the connections of trimeric building units.
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