A neutral Fe(III) compound exhibiting a two-step spin transition and dielectric anomalies.

The mononuclear ferric compound Fe(H-5-Cl-thsa-Me)(5-Cl-thsa-Me)-H2O (1) was synthesized and characterized using powder/single-crystal X-ray diffraction, Mossbauer spectroscopy, differential scanning calorimetry (DSC), and magnetic susceptibility measurements. This photo-responsive compound shows reversible, two-step spin-crossover behaviour. Moreover, dielectric anomalies were observed during the spin transitions, demonstrating the multifunctional properties of compound 1.