Mixed-valence states of iron long-chain carboxylate complexes

Mixed-valence oxo-centered trinuclear iron carboxylate complexes with long alkyl-chain fatty acid anions, myristate [Fe3O(O2CC13H27)(6)(py)(3)], palmi tate [Fe3O(O2CC15H31)(6)(py)(3)], stearate [Fe3O(O2CC17H35)(6)(py)(3)], and pyridine-solvated stearate [Fe3O(O2CC17H35)(6)(py)(3)]py, were studied by means of Fe-57 Mossbauer spectroscopy. Each nonsolvated complex showed a te mperature-dependent valence transformation between being valence-detrapped at room temperature (r.t.) and valence-trapped at low temperatures, while t he solvated stearate complex showed a trapped-valence state at any temperat ure below r.t, The complexes showed no thermal anomaly in their DSC thermog rams in the temperature range of 100-298 K, although the temperature depend ence of the Mossbauer parameters and the powder X-ray diffraction patterns suggested a phase transition in the solvated stearate complex at similar to 190 K. (C) 1999 Elsevier Science S.A. All rights reserved.