Correlating magnetic anisotropy with [Mo(CN)7]4− geometry of MnII–MoIII magnetic frameworks

Four new three-dimensional (3-D) coordination frameworks based on the heptacyanomolybdate(III) anion were prepared and characterised by magnetic measurements: {[MnII(imH)2]2[MnII(H2O)(imH)3][MnII(imH)4] [MoIII(CN)7]2·6H2O}n (1) (imH = imidazole), {[MnII(H2O)2(imH)]3[MnII(H2O)(imH)2][MoIII(CN)7]2·5H2O}n (2), {[MnII(Htrz)(H2O)2][MnII(Htrz)0.7(H2O)2.3][MoIII(CN)7]·5.6H2O}n (3) (Htrz = 1,2,4-triazole) and {[MnII(H2O)2]3[MnII(H2O)4][MoIII(CN)7]2·6H2O·2urea}n (4). All four compounds exhibit long-range ferrimagnetic ordering and exhibit an opening of their magnetic hysteresis loops at 1.8 K; 1 and 2 exhibit the highest coercive fields among all known [MoIII(CN)7]-based assemblies, 5000 and 4500 Oe respectively. The coercivity of 1–4 is correlated with the geometry of the heptacyanomolybdate(III) anion and the cyanide bridging pattern. A paramagnetic analogue of compound 1, {[MnII(imH)2]2[MnII(H2O)(imH)3][MnII(imH)4][ReIII(CN)7]2·6H2O}n (1Re), where the heptacyanomolybdate(III) anion is substituted by the diamagnetic heptacyanorhenate(III) anion is also reported which constitutes the first example of a coordination framework based on [ReIII(CN)7]4−.