Interpenetrated three-dimensional Mn^IIM^III ferrimagnets, [Mn(4dmap)₄]₃[M(CN)₆] ₂·10H₂O (M = Cr, Mn): Structures, magnetic properties, and pressure-responsive magnetic modulation

Two novel cyanide-bridged ferrimagnets, [Mn(4dmap)₄] ₃[M(CN)₆]₂-·10 H₂O (4dmap = 4-dimethylaminopyridine, M = Cr (1) and Mn (2)), have been prepared from the reaction of MnCl₂·4H₂O, a monodentate coligand (4dmap), with K₃[M(CN)₆]. X-ray crystallographic results show that these are isomorphous, and form a unique two-fold interpenetrated three-dimensional framework with a triconnected 6.10² net. The framework contains two types of one-dimensional channel: hexagonal channels based on a cyanide-bridged Mn₆M₆ hexagon, and triangle channels segmented by CN-Mn-NC linkages, which are filled with lattice water molecules. The dimethylamino groups of the 4dmap coligands are located around a pore and form the basic inner space. Variable-temperature X-ray powder diffraction and thermogravimetric analysis results show that the frameworks of both compounds are susceptible to dehydration through the loss of strongly hydrogen-bonded lattice water molecules. Magnetic measurements on both compounds show a ferrimagnetic ordering occurs at low temperature, T_c= 17 K for 1 and 6 K for 2. Application of hydrostatic pressure showed a positive effect on the magnetic ordering. Both values of T_c increased linearly, to 25 K for 1 and 15 K for 2 at 1.0 GPa. The magnetic properties of both compounds were reversibly modulated by the external stress.