A Mössbauer Spectroscopy Study of Dehydration of the Hydrate of a Neutral Spin-Crossover Fe(III) Complex Based on the Pyruvic Acid Thiosemicarbazone Ligand

The dehydration of the hydrate of the neutral spin-crossover- (S = 5/2 ↔ S = 1/2) complex [FeIII(Hthpy)(thpy)]·H2O (1) based on the pyruvic acid thiosemicarbazone ligand (H2thpy) has been studied by temperature-dependent 57Fe Mössbauer spectroscopy. It has been shown that the release of water from the structure of polycrystalline sample 1 in the temperature range 92–160°С is associated with the formation of the neutral complex [FeII(Hthpy)2] stabilized in the high-spin state (S = 2). A comparative analysis of the spectral parameters of complex 1 and the anhydrous neutral spin-crossover complex [FeIII(Hthpy)(thpy)] (2) has revealed that complex 2 retains its spectral characteristics when heated in air in a similar temperature range.