2D Bimetallic Oxalate-Based Ferromagnets with Inserted [Fe(4-Br-sal_2-trien)]~+ and [Fe(3-R-sal_2-trien)]~+ (R = Br, Cl and CH_3O) Fe~(III) Spin-Crossover Complexes

摘要

The syntheses, structures and magnetic properties of the compounds of formula [Fe~(III)(4-Br-sal_2-trien)][Mn~(II)Cr~(III)- (ox)_3]_(0.67)Cl_(0.33)?CH_3OH_solvate (1), [Fe~(III)(3-Br-sal_2-trien)]~- [Mn~(II)Cr~(III)(ox)_3]?(CH_3CN)_2 (2), [Fe~(III)(3-Cl-sal_2-trien)][Mn~(II)Cr~(III)- (ox)_3]?(CH_3OH)_2?(CH_3CN)_2 (3) and [Fe~(III)(3-CH_3O-sal_2-trien)][Mn~(II)Cr~(III)(ox)_3]?(CH_3OH)?(H_2O)_(1.5)?(CH_2Cl_2)_(0.5) (4) are reported. The four structures present a 2D honeycomb anionic layer formed by Mn~(II0 and CrIII ions linked through oxalate ligands and a cationic layer of the Fe~(III) 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 Fe~(III) 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 [Fe~(III)(sal_2-trien)]~- [Mn~(II)Cr~(III)(ox)_3]?(CH_2Cl_2). These results could help to clarify this rare property for a Fe~(III) complex.