A magneto - spectroscopic study of the 6A1 - 2T2 crossover in FE(III) complexes

Abstract

Two series of compounds: ferric dithiocarbamates and ferric monothio β-diketones, have been prepared during the course of this work, in order to investigate the 6A1 - 2T2 crossover in Fe(III). The current ideas and models are presented here and a series of experiments has been carried out to extend the model to its limits. Solid state and solution magnetic moments have been obtained for some dithiocarbamates, and these results have been compared directly with those obtained by consideration of N.M.R. temperature-dependent spectra. A series of monothio β-diketones from the literature has been fitted to the model and the results suggest that the model can readily accomodate crossover data from compounds other than dithiocarbamates. E.S.R. data is obtained for both series of compounds, and the monothio β-diketone results have been analysed in order to obtain some information about the ground state wavefunctions and the degree of distortion in the 2T2 state. Both E.S.R. and Mössbauer observations of the crossover have been made and reveal that the rate of exchange between high and low spin is comparatively slow for monothio β-diketones, whereas dithiocarbamates exchange at a rate that is much faster than can be detected by modern equipment.