Mössbauer spectroscopy studies of selected conducting polypyrroles

Abstract

Polypyrrole obtained by chemical oxidation of pyrrole in ethanol–water solution containing FeCl3 can be reduced chemically in Na+Naph−/THF solution and then reoxidized with FeCl3, SnCl4, and SbCl5. 5 7Fe and 1 1 9Sn Mössbauer spectra of the reaction products show only one type of iron and tin with Mössbauer parameters characteristic of FeCl− 4 and SnCl− 5. In the case of the oxidation with SbCl5, two nonequivalent antimony nuclei have been detected by 1 2 1Sb. The calculated isomer shift and quadrupole splitting values are consistent with SbCl− 6 and SbCl3. The resonant absorption in all three systems studied is strongly temperature dependent and can be observed only at temperatures significantly lower than RT. This behavior indicates a low Mössbauer lattice temperature and an extremely loose bonding between the inserted anions and polymer chains.