Stimuli Responsive Hybrid Magnets: Tuning the Photoinduced Spin-Crossover in Fe(III) Complexes Inserted into Layered Magnets

The insertion of a [Fe(sal(2)-trien)](+) complex cation into a 2D oxalate network in the presence of different solvents results in a family of hybrid magnets with coexistence of magnetic ordering and photoinduced spin-crossover (LIESST effect) in compounds [Fe-III(sal(2)-trien)][(MnCrIII)-Cr-II(ox)(3)]center dot CHCl3 (1 center dot CHCl3), [Fe-III(sal(2)-trien)][(MnCrIII)-Cr-II(ox)(3)]center dot CHBr3 (1 center dot CHBr3), and [Fe-III(sal(2)-trien)][(MnCr)-Cr-II(ox)(3)]center dot CH2Br2 (1 center dot CH2Br2). The three compounds crystallize in a 2D honeycomb anionic layer formed by Mn-II and Cr-III ions linked through oxalate ligands and a layer of [Fe(sal(2)-trien)](+) complexes and solvent molecules (CHCl3, CHBr3, or CH2Br2) intercalated between the 2D oxalate network The magnetic properties and Mossbauer spectroscopy indicate that they undergo long-range ferromagnetic ordering at 5.6 K and a spin crossover of the intercalated [Fe(sal(2)-trien)](+) complexes at different temperatures T-1/2. The three compounds present a LIESST effect with a relaxation temperature T-LIESST inversely proportional to T-1/2. The isostructural paramagnetic compound, [Fe-III(sal(2)-trien)][(ZnCrIII)-Cr-II(ox)(3)]center dot CH2Cl2 (2 center dot CH2Cl2) was also prepared. This compound presents a partial spin crossover of the inserted Fe-III complex as well as a LIESST effect Finally, spectroscopic characterization of the Fe-III doped compound [Ga0.99Fe0.01(sal(2)trien)][(MnCrIII)-Cr-II(ox)(3)]center dot CH2Cl2 (3 center dot CH2Cl2) shows a gradual and complete thermal spin crossover and a LIESST effect on the isolated Fe-III complexes. This result confirms that cooperativity is not a necessary condition to observe the LIESST effect in an Fe-III compound.