Spin-crossover in Fe(III)-Komplexen von Thiosemicarbazonen der 2-Oxo-Carbonsäuren

The Fe compounds (Et4N)2{[((TSP) (TSPH)Fe]2suc}3) and K[Fe(TSP) (TSPH)prop] · 3H2O3) were characterized by means of 57Fe Moessbauer spectroscopy and magnetic measurements. In the temperature region from 300 to 390 K the Fe(III) of both compounds undergoes a discontinuous transition from low spin state to high spin state, returning only slowly into low spin state after cooling to room temperature. This process causes a hysteresis behaviour of the magnetic values. The spin crossover is connected with a complex isomerization. Moessbauer spectra of the compounds show a significant asymmetry, which can be explained by relaxation effects according to Blume's theory.