2D Bimetallic Oxalate-Based Ferromagnets with Inserted [Fe(4-Br-sal2-trien)]+ and [Fe(3-R-sal2-trien)]+ (R = Br, Cl and CH3O) FeIII Spin-Crossover Complexes



The syntheses, structures and magnetic properties of the compounds of formula [FeIII(4-Br-sal2-trien)][MnIICrIII(ox)3]0.67Cl0.33·CH3OH_solvate (1), [FeIII(3-Br-sal2-trien)][MnIICrIII(ox)3]·(CH3CN)2 (2), [FeIII(3-Cl-sal2-trien)][MnIICrIII(ox)3]·(CH3OH)2·(CH3CN)2 (3) and [FeIII(3-CH3O-sal2-trien)][MnIICrIII(ox)3]·(CH3OH)·(H2O)1.5·(CH2Cl2)0.5 (4) are reported. The four structures present a 2D honeycomb anionic layer formed by MnII and CrIII ions linked through oxalate ligands and a cationic layer of the FeIII complexes intercalated between the 2D oxalate network. The main differences compared with previous 2D oxalate-based structures are the presence of double layers of cations in compounds 1, 3 and 4 and porous channels in the structures of 1 and 4 filled with disordered solvent molecules. The magnetic properties indicate that the inserted FeIII cations undergo an almost complete spin crossover above 300 K in 1 and a partial spin crossover in 3 and 4 that coexists with a ferromagnetic ordering of the oxalate network. In the case of 2, the inserted cation remains in the HS from 2 to 300 K. Therefore, 1, 3 and 4 are multifunctional compounds with coexistence of spin crossover and magnetic ordering. Conversely, photomagnetic characterization shows that 1 and 3 do not present a LIESST effect in contrast to the 2D compound [FeIII(sal2-trien)][MnIICrIII(ox)3]·(CH2Cl2). These results could help to clarify this rare property for a FeIII complex.