Spin Crossover and Thermochromism of Iron(II) Coordination Compounds with 1,2,4-Triazoles and Tris(pyrazol-1-yl)methanes

We review herein the synthesis and investigation of iron(II) coordination compounds with 1,2,4-triazoles or tris(pyrazol-1-yl)methanes as ligands. Both groups of complexes demonstrate thermally induced spin crossover accompanied by thermochromism [pink (magenta) <-> white color change]. Factors that influence the nature and temperature of the spin crossover are discussed.