Bimetallic Magnetic Material [Ni(diamine)₂]₂[Fe(CN)₆]X with Two-Dimensional Network Extended by Fe(III)-CN-Ni(II) Linkages

Abstract

Cyanide-bridged bimetallic assemblies [Ni(pn) 2 ] 2 [Fe(CN) 6 ]X·cat n H 2 O (X = ClO 4 - and n = 2 ( 1 ); X = BF 4 - and n = 2 ( 2 ); X = PF 6 - and n = 2 ( 3 )) and [Ni(1,1-dmen) 2 ] 2 [Fe(CN) 6 ]X· n H 2 O (X = ClO 4 - and n = 2 ( 4 ); X = BF 4 - and n = 3 ( 5 ); X = PF 6 - and n = 2 ( 6 ); X = CF 3 SO 3 - and n = 2 ( 7 ); X = BzO - and n = 6 ( 8 ); X = I - and n = 4 ( 9 ); X = N 3 - and n = 4 ( 10 ); X = NCS - and n = 1 ( 11 ); X = NO 3 - and n = 4 ( 12 )) have been prepared (pn = 1,2-propanediamine, 1,1-dmen = 1,1-dimethylethylenediamine). 7 crystallizes in a monoclinic space group P 2 1 / m (no. 11), with a = 10.300(6), b = 20.632(4), c = 10.352(7) Å, β = 109.45(4)°, V = 2074(1) Å 3 for Z = 4. 8 crystallizes in a triclinic space group P 1̄ (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) Å 3 for Z = 2. 10 crystallizes in triclinic space group P 1̄ (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) Å 3 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.