A three-dimensional manganese（Ⅱ）-substituted aluminum phosphate, Mn3Al6（PO4）12·4tren·11H2O[tren is tris（2-aminoethyl）amine], was synthesized hydrothermally. Its structure was determined by single-crystal X-ray diffraction analysis and further characterized by X-ray powder diffraction, ICP, TG analyses and magnetic susceptibility measurements. It crystallizes in the cubicsystem, space group I-43m（No. 217） with a=1.683 51（4）nm, V=4.771 4（2） nm3, Z=2, R1=0.043 9 and wR2=0.132 4[I>2σ（I）]. The open framework built up from strict alternation of TO4/AlO4 and PO4 tetrahedra through corner-sharing vertex oxygen atoms. It contains 12-membered ring channels. The Mn atoms of the framework are bivalence proved by magnetic susceptibility measurements.
A two-dimensional layered manganese(II) pyrophosphate, 2[Mn3(P2O7)2(H2O)2] (1), has been synthesized hydrothermally. Its structure is determined by single-crystal X-ray diffraction analysis. Its structure is built up by MnO6 octahedra and P2O7 units, with ammonium NH4+ cations residing in the interlayer regions. The manganese pyrophosphate layer consists of infinite chains of cis and trans edge sharing MnO6 octahedra linked by P2O7 units. Magnetic susceptibility measurements show that this compound exhibits ferrimagnetic-like ordering below 3.2 K. Further study shows that there are two possible superexchange pathways via the oxygen anions in Mn2+ ions. Owing to the different bridging modes of O2-, the competition between ferromagnetic interactions and antiferromagnetic interactions in Mn2+ ions results in the ferrimagnetic behavior of 1.
