MOSSBAUER SPECTROSCOPIC IDENTIFICATION OF THERMAL-DECOMPOSITION PRODUCTS IN IRON(III) CARBOXYLATES

A series of carboxylatoferrate (III) complexes have been synthesized w ith monocarboxylic and dicarboxylic acids. Mossbauer spectra of all th e complexes exhibit quadrupole doublets with Delta E(Q) = 0.36-0.88 mm s(-1), suggesting a distorted octahedral geometry. The complexes star t decomposing at approximate to 100 degrees C and finally yield a cons tant weight at < 500 degrees C. Mossbauer spectral studies of the inte rmediates and final products after heating at different temperatures y ield a complex pattern, suggesting the formation of one or two magneti c phases. Mossbauer spectra of the final products show two, six or eig ht lines with a central doublet, all indicating the formation of alpha -Fe2O3 of different particle sizes. It is proposed that decarboxylatio n occurs first, followed by the loss of one or two ligands, depending on the nature of the carboxylate and the heating temperature. The comp lex of pyridine-2,6-dicarboxylic acid shows an anomalous behavior.