Spin crossover in a tetranuclear Cr(III)-Fe(III)(3) complex

A novel heteronuclear exchange-coupled complex Cr(III)(CN)Fe(III)((5)L)](3)(CN)(3)] containing a pentadentate blocking ligand (5)L was synthesized. The X-ray structure shows that a meridional isomer applies with inequivalent Fe(III) centers. The complex exhibits a thermally induced spin crossover along with the exchange coupling. M?ssbauer spectra indicate a spin transition between S = (1)/(2) and S = (5)/(2) states although a considerable amount of Fe(III) centers stays high-spin at T = 6 K. The magnetization, the magnetic susceptibility, and the M?ssbauer data were fitted in one run with a spin crossover model taking into account exchange interactions among all metal centers.