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A Mn(II) salt and A+CN− under anaerobic conditions react to form 2‐D and 3‐D extended structured compounds of AmMnIIn(CN)m+2n stoichiometry. Here, the creation and characterization of this large family of compounds, for example AMnII3(CN)7, A2MnII3(CN)8, A2MnII5(CN)12, A3MnII5(CN)13, and A2MnII[MnII(CN)6], where A represents alkali and tetraalkylammonium cations, is reviewed. Cs2MnII[MnII(CN)6] has the typical Prussian blue face centered cubic unit cell. However, the other alkali salts are monoclinic or rhombohedral. This is in accord with smaller alkali cation radii creating void space that is minimized by increasing the van der Waals stabilization energy by reducing ∠Mn−N≡C, which, strengthens the magnetic coupling and increases the magnetic ordering temperatures. This is attributed to the non‐rigidity of the framework structure due the significant ionic character associated with the high‐spin MnII sites. For larger tetraalkylammonium cations, the high‐spin Mn sites lack sufficient electrostatic A+⋅⋅⋅NC stabilization and form unexpected 4‐ and 5‐coordinated Mn sites within a flexible, extended framework around the cation; hence, the size, shape, and charge of the cation dictate the unprecedented stoichio‐metry and unpredictable cation adaptive structures. Antiferromagnetic coupling between adjacent MnII sites leads to ferrimagnetic ordering, but in some cases antiferromagnetic coupling of ferrimagnetic layers are compensated and synthetic antiferromagnets are observed. The magnetic ordering temperatures for ferrimagnetic A2MnII[MnII(CN)6] with both octahedral high‐ and low‐spin MnII sites increase with decreasing ∠Mn−N≡C. The crystal structures for all of the extended structured materials were obtained by powder diffraction. [ABSTRACT FROM AUTHOR]

The reactions of MnII(O2CCH3)2 with NEt3Me+CN− and NEt2Me2+CN− form (NEt3Me)2MnII5(CN)12 (1) and (NEt2Me2)2MnII5(CN)12 (2), respectively. Structure model‐building and Rietveld refinement of high‐resolution synchrotron powder diffraction data revealed a cubic [a=24.0093 Å (1), 23.8804 Å (2)] 3D extended structural motif with adjacent tetrahedral and octahedral MnII sites in a 3:2 ratio. Each tetrahedral MnII site is surrounded by four low‐spin octahedral MnII sites, and each octahedral MnII site is surrounded by six high‐spin tetrahedral MnII sites; adjacent sites are antiferromagnetically coupled in 3D. Compensation does not occur, and magnetic ordering as a ferrimagnet is observed at Tc=13 K for 2 based on the temperature at which remnant magnetization, Mr(T)→0. The hysteresis has an unusual constricted shape with inflection points around 50 and 1.2 kOe with a 5 K coercivity of 16 Oe and remnant magnetization, Mr, of 2050 emuOe mol−1. The unusual structure and stoichiometry are attributed to the very ionic nature of the high‐spin N‐bonded MnII ion, which enables the maximization of the attractive van der Waals interactions through minimization of void space via a reduced ∠ MnNC. This results in an additional example of the AxMnIIy(CN)x+2y (x=0, y=1; x=1, y=3; x=2, y=1; x=2, y=2; x=2, y=3; x=3, y=5; and x=4, y=1) family of compounds possessing an unprecedented stoichiometry and lattice motif that are cation adaptive structured materials. [ABSTRACT FROM AUTHOR]

The reaction of MnII(O2CMe)2 and NaCN or LiCN in water forms a light green insoluble material. Structural solution and Rietveld refinement of high‐resolution synchrotron powder diffraction data for this unprecedented, complicated compound of previously unknown composition revealed a new alkali‐free ordered structural motif with [MnII4(μ3‐OH)4]4+ cubes and octahedral [MnII(CN)6]4− ions interconnected in 3D by MnII‐N≡C‐MnII linkages. The composition is {[MnII(OH2)3][MnII(OH2)]3}(μ3‐OH)4][MnII(μ‐CN)2(CN)4]⋅H2O=[MnII4(μ3‐OH)4(OH2)6][MnII(μ‐CN)2(CN)4]⋅H2O, which is further simplified to [Mn4(OH)4][Mn(CN)6](OH2)7 (1). 1 has four high‐spin (S=5/2) MnII sites that are antiferromagnetically coupled within the cube and are antiferromagnetically coupled to six low‐spin (S=1/2) octahedral [MnII(CN)6]4− ions. Above 40 K the magnetic susceptibility, χ(T), can be fitted to the Curie–Weiss expression, χ ∝(T−θ)−1, with θ=−13.4 K, indicative of significant antiferromagnetic coupling and 1 orders as an antiferromagnet at Tc=7.8 K. Structural solution and Rietveld refinement of high‐resolution diffraction data for an unprecedented, complicated compound of previously unknown composition revealed a new alkali‐free ordered structural motif with [MnII4(μ3‐OH)4]4+ cubes and octahedral [MnII(CN)6]4− ions interconnected in 3D. [ABSTRACT FROM AUTHOR]

The reaction of MnII and [NEt4]CN leads to the isolation of solvated [NEt4]Mn3(CN)7 ( 1) and [NEt4]2Mn3(CN)8 ( 2), which have hexagonal unit cells [ 1: R $\bar 3$ m, a=8.0738(1), c=29.086(1) Å; 2: P $\bar 3$ m1, a=7.9992(3), c=14.014(1) Å] rather than the face centered cubic lattice that is typical of Prussian blue structured materials. The formula units of both 1 and 2 are composed of one low- and two high-spin MnII ions. Each low-spin, octahedral [MnII(CN)6]4− bonds to six high-spin tetrahedral MnII ions through the N atoms, and each of the tetrahedral MnII ions are bound to three low-spin octahedral [MnII(CN)6]4− moieties. For 2, the fourth cyanide on the tetrahedral MnII site is C bound and is terminal. In contrast, it is orientationally disordered and bridges two tetrahedral MnII centers for 1 forming an extended 3D network structure. The layers of octahedra are separated by 14.01 Å ( c axis) for 2, and 9.70 Å ( c/3) for 1. The [NEt4]+ cations and solvent are disordered and reside between the layers. Both 1 and 2 possess antiferromagnetic superexchange coupling between each low-spin ( S=1/2) octahedral MnII site and two high-spin ( S=5/2) tetrahedral MnII sites within a layer. Analogue 2 orders as a ferrimagnet at 27(±1) K with a coercive field and remanent magnetization of 1140 Oe and 22 800 emuOe mol−1, respectively, and the magnetization approaches saturation of 49 800 emuOe mol−1 at 90 000 Oe. In contrast, the bonding via bridging cyanides between the ferrimagnetic layers leads to antiferromagnetic coupling, and 3D structured 1 has a different magnetic behavior to 2. Thus, 1 is a Prussian blue analogue with an antiferromagnetic ground state [ Tc=27 K from d( χT)/d T]. [ABSTRACT FROM AUTHOR]