Correlating magnetic anisotropy with [Mo(CN)] geometry of Mn-Mo magnetic frameworks.

Four new three-dimensional (3-D) coordination frameworks based on the heptacyanomolybdate(iii) anion were prepared and characterised by magnetic measurements: {[Mn(imH)][Mn(HO)(imH)][Mn(imH)] [Mo(CN)]·6HO} (1) (imH = imidazole), {[Mn(HO)(imH)][Mn(HO)(imH)][Mo(CN)]·5HO} (2), {[Mn(Htrz)(HO)][Mn(Htrz)(HO)][Mo(CN)]·5.6HO} (3) (Htrz = 1,2,4-triazole) and {[Mn(HO)][Mn(HO)][Mo(CN)]·6HO·2urea} (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 [Mo(CN)]-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, {[Mn(imH)][Mn(HO)(imH)][Mn(imH)][Re(CN)]·6HO} (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 [Re(CN)].