Novel Transition Metal Oxalatophosphates with a Two-Dimensional Honeycomb Structure: (H3TREN)[M2(HPO4)(C2O4)2.5]·3H2O (M = MnII and FeII, TREN = Tris(2-aminoethyl)amine)

Two new layered transition metal oxalatophosphates, (H3TREN)[M2(HPO4)(C2O4)2.5]·3H2O (M = MnII and FeII), have been synthesized by hydrothermal methods in the presence of a structure-directing organic amine, tris(2-aminoethyl)amine, and characterized by single-crystal X-ray diffraction and magnetic susceptibility. They are the first metal oxalatophosphates which adopt a two-dimensional honeycomb structure with the organic cations and water molecules intercalated in between. Within a layer, there are 12-membered pores made from 6 Mn, 1 phosphate, and 5 oxalate units. Measurements of field dependence of magnetization and variable-temperature susceptibilities under different fields were performed on a polycrystalline sample of the manganese compound. The results indicate a phase transition from a paramagnetic to an antiferromagnetic coupled state at about 12 K. Crystal data for the manganese compound follow: triclinic, space group P (No. 2), a = 8.8385(6) (angstrom), b = 9.0586(6) (angstrom), c = 16.020(1) (angstrom), (alpha)= 77.616(1), (beta) = 83.359(1), (gamma)= 68.251(1), and Z = 2. Crystal data for the iron compound are the same as those for the manganese compound except a = 8.7776(9) (angstrom), b = 8.9257(9) (angstrom), c = 15.884(2) (angstrom), (alpha)= 78.630(2), (beta) = 84.018(2), and (gamma) = 67.372(2).