Mössbauer Spectra of Some Iron Complexes

Abstract

Mössbauer spectra were obtained for the following coordination compounds: iron phthalocyanine, ferrocene, iron carbonyl, iron III acetylacetonate, and iron II acetylacetonate dipyridine; for the following complex ion salts iron II trisphenanthroline chloride, iron III EDTA (monosodium salt), iron II EDTA, hemin, ferricium picrate, sodium nitroprusside, and some ferro- and ferricyanides. The isomer shift (relative to stainless steel) for iron II has the value expected for an inorganic ion only for iron II EDTA. In the other complexes the shifts are about 0.4 mm/sec, except ferrocyanide which is near zero. For iron III only hemin and ferricyanide have unusually small isomer shifts. The large negative isomer shift in sodium nitroprusside suggests iron IV. Except for ferrocyanide quadrupole splittings occurred in iron of valence 0, II, and IV and were observed for both spin-paired and spin-unpaired complexes. Splittings varied widely, however not exceeding those for inorganic ferrous salts. Sodium ferricyanide showed an unexpected quadrupole splitting. Other iron III complexes gave broad and unsymmetrical spectra.