Three isomorphous compounds M(CHOO)3[NH2(CH3)2] (M) Mn(1•Mn), Co(2•Co), Ni(3•Ni)) have been synthesized in solvothermal conditions. Single-crystal X-ray diffraction shows that they are all crystallized in the trigonal space group R 3hc with small differences in the lattice parameters. Bridged by the three-atom single-bridge CHOO-, M ions form a three-dimensional distorted perovskite-like structure with dimethylamine (DMA) cations located in the cages of the network. Based on the magnetic data, these three 3D compounds are weak ferromagnets with the critical temperature Tc) 8.5 K (1•Mn), 14.9 K (2•Co), and 35.6 K (3•Ni), and for 2•Co and 3•Ni, spin reorientation might take place at 13.1 and 14.3 K, respectively. At 1.8 K, hysteresis loops can be observed for all three compounds with the coercivity field ca. 90 Oe (1•Mn), 920 Oe (2•Co), and 320 Oe (3•Ni). The canting angles are estimated to be 0.08º 0.5º, and 0.6º for 1•Mn, 2•Co, and 3•Ni, respectively. The magnetic coupling between MnII ions in 1•Mn was estimated based on the model developed by Rushbrook and Wood for a Heisenberg antiferromagnet on a simple cubic lattice and the best fit gives J)-0.23cm-1. At the same time, according to molecular field theory of antiferromagnetism, the J values for compounds 1•Mn, 2•Co, and 3•Ni were estimated to be -0.32cm-1, -2.3cm-1, and -4.85cm-1, respectively. The spin cant in these compounds may originate from the noncentrosymmetric character of the three-atom single-bridge CHOO-. Furthermore, amorphous materials 4•Mn238, 5•Mn450, 6•Co320, and 7•Ni300 were prepared from precursors 1-3 under an argon atmosphere at different temperatures according to the thermogravimetric analyses. As an interesting result, 5•Mn450 was confirmed to be an amorphous form of Mn3O4 with a considerably large coercivity field HC) 4.1 kOe at 30 K compared to that value (250 Oe) for bulk Mn3O4.

Much attention is currently being devoted to the design and synthesis of molecular magnetic materials exhibiting spontaneous magnetization. The main synthetic strategy is virtually to use and connect two paramagnetic building blocks (bricks) to generate polynuclear or extended arrays. Extended arrays of high dimensionalities may exhibit higher ordering temperatures due to the increased number of interacting neighbors. A representative example is the cyano-bridged three-dimensional (3D) Prussian blue-type complexes constructed from hexacyanometalate(Ⅲ) and simple transition metal building blocks.1 One of these materials exhibits long-range magnetic ordering at Tc as high as 372 K.1c Thus far, a number of Prussian blue analogues of different dimensionalities have been synthesized and characterized structurally and magnetically. 2,3 These studies have shown that the lowdimensional materials have Tc values generally lower than that of the corresponding 3D analogues, and the few hybrid 3D arrays.