Abrupt Spin Transition with Thermal Hysteresis of Iron(III) Complex [Fe~(III)(Him)_2(hapen)]AsF_6 (Him = Imidazole, H_2hapen = N,N'?Bis(2-hydroxyacetophenylidene)ethylenediamine)

摘要

The solvent-free spin crossover iron(III) complex [Fe~(III)(Him)_2(hapen)]AsF_6 (Him = imidazole, H_2hapen = N,N'-bis(2-hydroxyacetophenylidene)ethylenediamine), exhibiting thermal hysteresis, was synthesized and characterized. The Fe~(III) ion has an octahedral coordination geometry, with N_2O_2 donor atoms of the planar tetradentate ligand (hapen) and two nitrogen atoms of two imidazoles at the axial positions. One of two imidazoles is hydrogen-bonded to the phenoxo oxygen atom of hapen of the adjacent unit to give a hydrogen-bonded one-dimensional chain, while the other imidazole group is free from hydrogen bonding. The temperature dependencies of the magnetic susceptibilities and Mo?ssbauer spectra revealed an abrupt spin transition between the high-spin (S = 5/2) and low-spin (S = 1/2) states, with thermal hysteresis.