[NH<sub>4</sub>]<sub>2</sub>Mn<sub>3</sub>(H<sub>2</sub>O)<sub>4</sub>[Mo(CN)<sub>7</sub>]<sub>2</sub>·4H<sub>2</sub>O: Tuning Dimensionality and Ferrimagnetic Ordering Temperature by Cation Substitution
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[NH4]2Mn3(H2O)4[Mo(CN)7]2·4H2O (1) has been synthesized by slow diffusion of aqueous solutions containing K4[Mo(CN)7]·2H2O, [Mn(H2O)6](NO3)2, and (NH4)NO3. Compound 1 crystallizes in the monoclinic C2/c space group. The basic motif of the three-dimensional structure consists of a Mo1−Mn1 gridlike sheet parallel to the bc plane. Two of these sheets are connected through CN−Mn2−NC linkages to form a bilayer reminiscent of the K2Mn3(H2O)6[Mo(CN)7]2·6H2O (2) two-dimensional structure. In 1, [NH4]+ cations allow these bilayers to be connected through direct Mo1−CN−Mn1 bridges to form a three-dimensional network, whereas in 2, they are isolated by (H2O)K+ cations. As shown by the magnetic measurements, this increase of dimensionality by counterion substitution induces an enhancement of the ferrimagnetic critical temperature from 39 K in 2 to 53 K in 1.
