The dependence of Mössbauer isomer shifts on magnetic moments in solvated tris-dithiocarbamates on iron(III)

Iron(III) Spin Crossover Compounds

“…The spectra exhibit a single, quadrupole-split absorption, comparable to these observed for Fe(III) dithiocarbamates. While a linear correlation between the 57 Fe Mössbauer isomer shifts and the magnetic moments of solvated Fe(III) dithiocarbamates could be established [40], no such correlation is clearly evident in the limited series of thioselenoand diselenocarbamates studied by Dietzsch [71]. Although variations are noted for specific organic substituents, the general trend for the average isomer shifts is OSCNR 2 < S 2 CNR 2 % SSeCNR 2 % Se 2 CNR 2 .…”

“…The rapid inter-conversion of spin states-faster or comparable to the lifetime of the 57 Fe nucleus (t=1.410 7 s)-in those materials prevents the observation of separate lines for high spin and low spin molecules. This feature allowed, on the other hand, the establishment of a linear correlation between the 57 Fe Mössbauer isomer shifts and the magnetic moments of solvated Fe(III) dithiocarbamates [40].…”

“…Unlike the normal situation in iron(II) and also in many other iron(III) systems, 57 Fe Mössbauer spectroscopy generally fails to give clear evidence of the simultaneous existence of the two electronic states. The 57 Fe Mössbauer spectra of the dithiocarbamate systems exhibit only a single quadrupole doublet with broad line widths within the temperature range of the spin crossover [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. The rapid inter-conversion of spin states-faster or comparable to the lifetime of the 57 Fe nucleus (t=1.410 7 s)-in those materials prevents the observation of separate lines for high spin and low spin molecules.…”