Spin crossover Fe(III) complexes with tetradentate Schiff base ligands

Abstract Fe(III) complexes are capable of exhibiting a spin transition between high spin and low spin states under the influence of external stimuli, such as temperature, pressure, photoradiation, phase change, etc . In this case, the structural and magnetic characteristics change without changing the composition. The creation of new spin-crossover compounds with predetermined switching properties is important for applied purposes. This review collects and summarizes the results of the synthesis and study of the spin-crossover properties of Fe(III) complexes with symmetric tetradentate Schiff bases. The influence of the molecular structure on the spin-crossover properties is considered. A unique feature of tetradentate ligands is the possibility of obtaining both mononuclear and polynuclear Fe(III) complexes on their basis. The presence of an axial ligand is an additional channel for controlling the spin-crossover properties in addition to equatorial ligands, counterions, and solvated molecules.