Spin-crossover change from gradual to abrupt types for an iron(III) Complex

Iron(III) spin-crossover compound with acpa ligand [Fe-(acpa) 2 ]ClO 4 (1) was prepared and characterized by single-crystal X-ray diffraction, Mossbauer spectra, and magnetic susceptibilities, where acpa is a tridentate ligand derived from acetylacetone and 2-aminomethylpyridine. The iron(III) compound 1 displayed a structural phase transition at 250 K, and the spin-crossover behavior for 1 changed from gradual to abrupt before and after the structural phase transition.