Bimetallic magnetic material [Ni(diamine)₂]₂(Fe(CN)₆]X with two-dimensional network extended by Fe(III)-CN-Ni(II) linkages

Cyanide-bridged bimetallic assemblies O (X = ClO₄^- and n = 2 (1); X = BF₄^- and n = 2 (2); X = PF₆^- and n = 2 (3)) and [Ni(1,1-dmen)₂]₂[Fe(CN)₆]X·nH₂O (X = ClO₄^- and n = 2 (4); X = BF₄^- and n = 3 (5); X = PF₆^- and n = 2 (6); X = CF₃SO₃^- and n = 2 (7); X = BzO^- and n = 6 (8); X = I^- and n = 4 (9); X = N₃^- and n = 4 (10); X = NCS^- and n = 1 (11); X = NO₃^- and n = 4 (12)) have been prepared (pn = 1,2-propanediamine, 1,1-dmen = 1,1-dimethylethylenediamine). 7 crystallizes in a monoclinic space group P2₁/m (no. 11), with a = 10.300(6), b = 20.632(4), c = 10.352(7) Å, β = 109.45(4)°, V = 2074(1) ų for Z = 4. 8 crystallizes in a triclinic space group P1 (no. 2), a = 10.413(6), b = 22.060(6), c = 10.377(3) Å, α = 101.78(2), β = 95.71(4), γ = 77.29(3)°, V = 2272(1) ų for Z = 2. 10 crystallizes in triclinic space group P1 (no. 2), a = 10.314(1), b = 10.374(1), c = 10.233(1) Å, α = 93.23(1), β = 106.15(1), γ = 86.37(1)°, V = 1045.0(2) ų for Z = 2. In each compounds [Fe(CN)₆]^3- coordinates to four [Ni(1,1-dmen)₂]²⁺ cations through four cyano nitrogens on a plane, providing a 2-D sheet of a square structure extended by Fe-CN-Ni linkages. The square with four Fe(III) ions at the corners and four trans Ni(II) on the edges shows a slight distortion to a rhombus. A ferromagnetic interaction operates within the sheet in all the compounds. The overall magnetic property is governed by the intersheet separation: a small intersheet separation provides metamagnets (1, 2, 3, 4, 6, 11) owing to intersheet antiferromagnetic interaction, whereas a large intersheet separation (>10 Å) provides ferromagnets (5, 7, 8, 9, 10, 12). The ferromagnets became metamagnets on dehydration owing to shortening of the intersheet separation.