Direct measurement of the high-spin and low-spin bond lengths and the spin state population in mixed spin state systems: an FeK-edge XAFS study of iron(III) dithiocarbamate complexes

A combination of Fe K-edge XAFS and advanced data analysis methods has been used to determine the Fe-S distances and spin state population in iron(III) dithiocarbamate spin crossover complexes. This new approach allows for the first direct determination of Fe-S bond lengths (2.44(2) Angstrom high-spin, 2.30(2) Angstrom low-spin) for both spin state isomers in mixed spin systems in contrast to single crystal X-ray crystallographic determinations where only the weighted average of the HS and LS values is observed. The agreement between XAFS and magnetic susceptibility derived values of the spin state populations is very good. (C) 1999 Elsevier Science S.A. All rights reserved.