Mössbauer spectroscopic studies of spin crossover in tris(N, N′-dialkyldithiocarbamato) iron (III) complexes: effect of alkyl substituents

Abstract

Spin crossover behavior in tris(N,N′-dialkyldithiocarbamato) iron(III) complexes with varying alkyl groups has been studied by variable temperature magnetic moment and Mossbauer spectral studies. All the complexes may be divided into three broad groups; high spin (μ eff > 4.8 BM), intermediate spin (μ eff = 3.5 − 4.6 BM) and low spin (μ eff < 3.2 B.M). Room temperature (RT) Mossbauer spectra exhibit an asymmetric doublet resolved into two doublets corresponding to high and low spin states. Estimated % contributions of HS and LS states and calculated μ eff were comparable with the experimentally determined values. It has been shown that some complexes undergo spin crossover, 6A1g→2T2g whereas others exhibit spin transitions 6A1g →4T1g or 4T1g → 2T2g. IR spectra show characteristic ν (Fe − S) bands in the region 208–285 (HS) and 311–380 cm − 1 (LS). Nature of alkyl groups affects the spin state.