Heterometallic {DyIII2FeII2} Grids with Slow Magnetic Relaxation and Spin Crossover

The assembly of molecules simultaneously exhibiting slow magnetic relaxation and spin crossover (SCO) behaviors at the molecular level is a fascinating challenge for chemists. The synthesis strategy of combining 3d and 4f ions in a molecule is a very promising route to a dual magnetic system. With this goal in mind, a series of mixed-metal structures, namely [Dy2Fe2(H2L)4(OH)6](NO3)4·12CH3OH·6H2O (1), [Dy2Fe2(H2L)4(OH)6]Cl4·2CH3OH·20H2O (2), [Dy2Fe2(H2L)4(OH)6]Cl4·4CH3OH·20H2O (3) and [Dy2Fe2(H2L)4(NO3)3CH3O](NO3)5(CF3SO3)·6CH3OH·H2O (4) containing a versatile Schiff-base ligand N′-((E)-pyridin-2-ylmethylene)-6-(2-((E)-pyridin-2-ylmethylene)hydrazinyl)nicotinohydrazide (H2L), have been synthesized and characterized. Alternating current (ac) susceptibility measurements reveal that complexes 1–4 exhibit a slow magnetic relaxation behavior. More importantly, complexes 2 and 3 exhibit one- and two-step SCO behaviors, respectively. To our knowledge, this is the first report on 3d–4f structures that exhibit the dual function of slow magnetic relaxation and SCO behaviors to date.