Mössbauer spectroscopy studies of selected conducting polypyrroles

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. 57Fe and 119Sn Mossbauer spectra of the reaction products show only one type of iron and tin with Mossbauer parameters characteristic of FeCl−4 and SnCl−5. In the case of the oxidation with SbCl5, two nonequivalent antimony nuclei have been detected by 121Sb. 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 Mossbauer lattice temperature and an extremely loose bonding between the inserted anions and polymer chains.