Heterometallic {Dy III2Fe II2} grids with slow magnetic relaxation and spin crossover

Abstract

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.