The insertion of a [Fe(sal₂-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(sal₂-trien)][Mn^IICr^III(ox)₃]·CHCl₃ (1·CHCl₃), [Fe^III(sal₂-trien)][Mn^IICr^III(ox)₃]·CHBr₃ (1·CHBr₃), and [Fe^III(sal₂-trien)][Mn^IICr^III(ox)₃]·CH₂Br₂ (1·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(sal₂-trien)]⁺ complexes and solvent molecules (CHCl₃, CHBr₃, or CH₂Br₂) 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(sal₂-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(sal₂-trien)][Zn^IICr^III(ox)₃]·CH₂Cl₂ (2·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 [Ga_0.99Fe_0.01(sal₂trien)][Mn^IICr^III(ox)₃]·CH₂Cl₂ (3·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.

Photoswitching of the dielectric constant has been observed for the first time in the spin-crossover complex [Fe(L)(CN)₂]·H₂O (L=2,13-dimethyl-6,9-dioxa-3,12,18-triazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene, see picture). The electrical detection of a photoinduced change in spin state could allow the use of such complexes in optical information-storage devices.