Molecular Magnetism in Manganese Dicyanamide Extended Network Structures

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Abstract
Dicyanamide, dca− (N(CN)2 −), forms an extended rutile-like single net in the binary complex, MnII(dca)2, in which dca groups bridge the MnII ions via the nitrile and amide nitrogen atoms. A trihydrate, which forms in the synthesis, displays an unusual structure consisting of square channels, formed by sheets of Mn(dca)2(H2O)2, into which are inserted linear chains of Mn(dca)2(H2O)2. Clathrated water molecules form H-bonded networks with the coordinated water and dca species. This trihydrate displays weak antiferromagnetic coupling between the high-spin Mn(II) ions without long-range ordering. Mn(dca)2 also displays weak antiferromagnetic coupling, but with an unusual magnetic phase transition being noted at Tc = 16K, particularly in low applied-fields. Dehydration of Mn(dca)2·3H2O yields Mn(dca)2 with the same magnetic transition at 16K.