Ligand 4-X pyridine (X = Cl, Br, I) dependence in Hofmann-type spin crossover complexes: Fe(4-Xpyridine)2[Au(CN)2]2

•Novel spin crossover complexes Fe(4-Xpy)2[Au(CN)2]2 with axial 4-X pyridine ligands (X = Cl, Br, and I).•The halogen-element dependence in the lattice parameters on the magnetic properties.•Structure parameters determined by EXAFS of Fe K edge and Au Ledge.•Aurophilic interaction studied.

We synthesize the novel spin crossover (SCO) complexes using Fe–Au based compounds bridged by cyanides with a variety of axial ligands. The complexes consist of the bridges by cyanide-based networks of Fe2+ and [Au(CN)2]− in Hofmann-type two dimensional systems with axial 4-X pyridine ligands (X = Cl, Br, and I): Fe(4-Xpy)2[Au(CN)2]2. We investigate systematically the halogen-element dependence in the lattice parameters on the magnetic properties. X-ray absorption fine structure spectroscopies depict the element specific spectral changes between high-spin and low-spin transitions in the Fe sites. The relationship between the lattice volume and SCO transitions is discussed in details.

Graphical abstractWe synthesize the novel spin crossover complexes Fe(4-Xpy)2[Au(CN)2]2 with axial 4-X pyridine ligands (X = Cl, Br, and I). We investigate systematically the halogen-element dependence in the lattice parameters on the magnetic properties.Figure optionsDownload full-size imageDownload as PowerPoint slide