6533b873fe1ef96bd12d4d43

RESEARCH PRODUCT

Stimuli responsive hybrid magnets : tuning the photoinduced spin-crossover in Fe(III) complexes inserted into layered magnets

subject

description

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)][Mn^{II}Cr^{III}(ox)_3]·CHCl_3 (1·CHCl_{3}) [Fe^{III}(sal_{2} trien)][Mn^{II}Cr^{III}(ox)_{3}]·CHBr_{3} (1·CHBr_{3}) and [Fe^{III}(sal_{2} trien)][Mn^{II}Cr^{III}(ox)_{3}]·CH_{2}Br_{2} (1·CH_{2}Br_{2}). 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 (CHCl_{3} CHBr_{3} or CH_{2}Br_{2}) intercalated between the 2D oxalate network. The magnetic properties and Mössbauer 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)][Zn^{II}Cr^{III}(ox)_{3}]·CH_{2}Cl_{2} (2·CH_{2}Cl_{2}) 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 [Ga_{0.99}Fe_{0.01}(sal_{2}trien)][Mn^{II}Cr^{III}(ox)_{3}]·CH_{2}Cl_{2} (3·CH_{2}Cl_{2}) 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.