Two new diamine templated lanthanum sulfates, La2(H2O)2(C4H12N2)(SO4)4and La2(H2O)2(C2H10N2)3(SO4)6·4H2O, with 3D and 2D crystal structures

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Abstract
Two new lanthanum sulfates have been synthesised under hydrothermal conditions in the presence of piperazine or ethylenediamine. The compounds have been structurally characterised from single-crystal X-ray diffraction. La2(H2O)2(C4H12N2)2(SO4)4, 1, and La2(H2O)2(C2H10N2)3(SO4)6·4H2O, 2, crystallise with monoclinic symmetry, space group P21/c. Compound 1 exhibits a three-dimensional anionic open-framework constituted by lanthanum atoms and sulfate groups. The charge compensation is ensured by the presence of piperazinium cations occluded in the cavities of the structure. Compound 2 has a layered structure, built from inorganic anionic sheets of lanthanum sulfates between which are located the ethylenediammonium cations and water molecules. The thermal behaviour of the two compounds has been studied by temperature-dependent powder X-ray diffraction and thermal analyses. Intermediates have been characterised during the dehydration stages. The decomposition temperature of the diamines is also discussed with regard to their hydrogen bonding to the framework. The products obtained at the final stages of the decomposition are La2(SO4)3 and La2O2SO4.