A Tripodal Ligand Containing Three Imidazole Groups Inducing Spin Crossover in Both Fe(II) and Fe(III) Complexes; Structures and Spin Crossover Behaviors of the Complexes

A tripodal hexadentate ligand containing three imidazole groups gives spin-crossover iron complexes in both the +II and the +III oxidation states. The tetrafluoroborate salt of the Fe(II) complex shows a gradual spin transition in the temperature range 110–270 K. The corresponding Fe(III) complex shows a spin transition above 150 K, and at 300 K ca. 87% of the Fe(III) ion is in the high-spin state.