THE ANOMALOUS MOSSBAUER-SPECTRA OF TRIS(DIETHANOLDITHIOCARBAMATO)IRON(III) - SOLVATE EFFECTS

Attempts to repeat the previously reported preparation of Fe(S2CN(CH2CH2OH)2)3.3H2O from aqueous solution always yielded the unsolvated complex which displayed a normal two-line Mossbauer spectrum similar to those displayed by Fe(S2CN(CH2CH2OH)2)3 prepared in non-aqueous media. Contrary to previous reports, heating the sample did not produce an unsolvated sample, but instead, resulted in decomposition as indicated by elemental analysis, TGA and Mossbauer studies. In contrast to earlier reports, Fe(S2CN(CH2CH2OH)2)3 was successfully recrystallized from acetone and methanol. Each of these recrystallized complexes was, for the most part, quite ordinary in its elemental analysis, room-temperature magnetic moment (predominantly high spin) and Mossbauer spectrum. However, when Fe(S2CN(CH2CH2OH)2)3 prepared from ethanolic solution is recrystallized from methanol without heating during the removal of the methanol, the resulting complex yields a four-line Mossbauer spectrum at 77 K (isomer shifts: 0.726, 0.770 mm/s; quadrupole splittings: 1.18, 0.318 mm/s, respectively). The elemental analysis, room-temperature magnetic moment and EPR spectra of this complex were in accord with a predominantly high-spin, spin-crossover complex without sufficient solvate molecules to be detectable by elemental analysis. A detailed, temperature-dependent series of Mossbauer spectra are reported for this complex. These results are discussed on the basis of effects of small amounts of solvate molecules on the spin-crossover rate of these complexes and compared to reports of four-line Mossbauer spectra for Fe(S2CN(CH2)4O)3.CH2Cl2 at 77 K.