Very Anisotropic 2D Molecular Magnetic Materials Based on Pentagonal Bipyramidal Heptacyanidorhenate(IV)

The first neutral 2D heterometallic assemblies based on orbitally degenerate heptacyanidorhenate(IV) were prepared and structurally characterized. An analysis of the magnetic data for the polycrystalline samples of Ph$_4$P[{Mn(acacen)}$_2$Re(CN)$_7$]·Solv (1) and PPN[{Mn(acacen)}$_2$Re(CN)$_7$]·Solv (2) have shown that both materials display slow magnetic relaxation at temperatures below 10 and 21 K for 1 and 2, respectively. Despite the presence of the same molecular magnetic modules that make up the anionic layers, the studied 2D networks differ significantly in magnetic anisotropy, having a small coercive field (0.115 T) for 1 and a large one (~2.5 T) for 2 at 2 K. In addition, for both polymers a M(H) value does not saturate at the maximum available field of 7 T, and the material 2 is a metamagnet. This intriguing difference originates from the cooperative anisotropic spin interaction in Re$^{IV}$−CN−Mn$^{III}$ pairs and the zero field splitting (ZFS) effect of Mn$^{III}$ ions with a noncollinear alignment of the local magnetic axes in crystals of the compounds.