Comparison of one-, two-, and three-dimensional iron phosphates containing ethylenediamine

A new two-dimensional (2d) iron phosphate, (C2N2H10)Fe2O(PO4)2, has been synthesized under hydrothermal conditions in the system of FeCl3-H3PO4-C2N2H8-H2O. The crystal data is: space group P21/c, a=10.670(1) A, b=10.897(1) A, c=9.918(1) A, β=105.632(1) deg. , Z=4. The layered structure consists of double sheet layers, of composition Fe2O(PO4)2, built from FeO5 trigonal bipyramids and PO4 tetrahedra. The amine holds the layers together via H-bonding. The study of the magnetic properties reveals two magnetic transitions at 160 and 30 K with spin-glass-like behavior below 160 K. By varying the hydrothermal conditions, three other iron phosphates were synthesized: the one-dimensional (1d) (C2N2H10)Fe(HPO4)2(OH)·H2O, the 2d (C2N2H10)Fe2(PO4)2(OH)2, and the three-dimensional (3d) (C2N2H10)2Fe4O(PO4)4·H2O. The 1d compound can be used as the starting reagent in the synthesis of both the 2d compound and the 3d lipscombite Fe3(PO4)2(OH)2 due to the similar building blocks in their structures. In the 3d phosphate (C2N2H10)2Fe4O(PO4)4·H2O, manganese can substitute for half of the iron atoms. Magnetic study shows ordering transitions at about 30 K, however, manganese substitution depresses the magnetic ordering temperature