The Pivotal Role of Mössbauer Spectroscopy in the Characterization of Prussian Blue and Related Iron Cyanide Complexes

For 50 years, 57Fe Mössbauer spectroscopy has played a pivotal role in the characterization of Prussian blue complexes and many related iron cyanide complexes, a pivotal role that is extensively illustrated in this paper. For the benefit of the young Mössbauer spectroscopists, the successes, the failures, and the pitfalls reported in the literature are discussed. The successes include the unquestionable distinction of iron oxidation and spin states in Prussian blue and the determination that Prussian blue and Turnbull's blue are the same. The failures include the distinction between low-spin FeII and high-spin FeIIIcations in Berlin green. The pitfalls include many, sometimes poorly determined, hyperfine parameters that have been reported for complexes whose stoichiometry is either unknown or unspecified and even sometimes incorrect.