Construction And Magnetic Property Of The Molecular Magnet Using (NEt₄)₃Fe(CN)₆ As The Building Block

Based on the structural versatility of schiff base complexes and the importance of the C≡N group as the bridging ligand to transfer electron, we have focused on the design and synthesis of new compounds by use of the Schiff base complexes and (NEt4)3Fe(CN)6 as building blocks. Some new multinuclear or supramolecular compounds were obtained. The components and structure were determined by the results of the element analysis, IR, electronic spectrum and thermal analysis. The ligands of the mononuclear complexes are the schiff base ligands by reacting o-phenlyenediamine, ethylenediamine and diethylene tramine with salicylaldehyde series. Because of the smaller steric effect of the ethylenediamine and diethylene tramine than o-phenlyenediamine, and the rigidity of benzyl, the o-phenlyenediamine series ligands were the large conjugated systems. So the structure of the goal compounds from such Schiff base mononuclear compounds and (NEt4)3Fe(CN)6 were expected to be different. The results are that the ethylenediamine and diethylene tramine series compounds were cyanide－bridged molecular magnets, and that the o-phenlyenediamine series were supramolecular compounds connected by hydrogen bonding. The magnetic properties between the metal ions were expected to be ferromagnetic or antiferromagnetic coupled.The single crystal of goal compound C1 of o-phenlyenediamine series was obtained and analyzed by X－ray diffraction method. And the magnetic susceptibilities of C1, C7 of the ethylenediamine series, C8 and C10 of diethylene tramine series were discussed. The chemical formular of C1 is [NEt4][Mn(C20H14N2O2)(H2O)2]2 [Fe(CN)6]·H2O·CH3OH (C20H14N2(OH)2 is N,N'-bis (salicylidene)-1,2-diamino- benzene). The crystal belongs to triclinic system, space group Pī,with unit cell dimensions a＝1.2150(4) nm, b＝1.4834(6) nm, c＝1.6625(6) nm, α＝81.896(7)°, β＝76.980(8)°, γ＝81.120(6)°, V＝2.872(2) nm3, Z＝2, DC＝1.388 g·cm－3, F(000)＝1250. Each parts comprised of the compound are helded together by hydrogen bonding and formed the network supramolecular structure. The magnetic susceptibilities result of C1 suggests an antiferromagnetic interaction between Mn(III)(d4,H.S) and Fe(III)(d5+,L.S) ions through the hydrogen bonding with J＝－19.4 cm－1, g＝2.3,θ＝－11.2 K。The magnetic susceptibility for C7, C8 and C10was measured by a SQUID magnetometer under the applied magnetic field of 1 kOe . The result are g＝2.1,J＝5.1 cm－1,θ＝－2.4 K for C7 ([NEt4][Mn(C18H18N2O2)(H2O)]2[Fe(CN)6]·2H2O) (C18H18N2(OH)2 is N,N'－bis(5-methyl－salicylidene)ethylenediamine) g＝2.2,J＝4.8 cm－1,θ＝－2.2 K for C8 ([NEt4][Mn(C18H19N3O2)]2[Fe(CN)6]·2H2O·CH3OH] (C18H19N3(OH)2 is N,N'－bis(salicylidene) diethylene tramine), and g＝1.8,J＝2.8 cm－1,θ＝－2.4 K for C10 ([NEt4][Fe(C18H19N3O2)]2[Fe(CN)6]·2H2O·2CH3OH]), respectively．These all suggest the ferromagnetic interaction.The curves of the magnetic moment verse temperature for C7, C8 and C10 all have a maximum value at low temperature. Such phenomenon suggests the intramolecular antiferromagnetic interaction.