Yu. Maeda

Mossbauer study of polythiophene and its derivatives

Summary form only given. Polythiophene and its derivatives are highly conducting polymers when doped with appropriate chemical species such as iodine or FeCl/sub 3/. We have investigated the chemical structure of the dopants in these polymers using / sup 129/I and /sup 57/Fe, which are Mossbauer nuclei of good resolution. It has been found that the iodine in these polymers exists as linear forms of triiodide and pentaiodide anions and that the abundance ratio of triiodide decreases with increasing of the doping level. Since the polymers were doped with the iodine of neutral molecules, these anions are created by electron transfer between the polymers and the dopants. Our experimental results are consistent with the proposed mechanism of the electric conductivity which is due to migration of polarons on the polymer chains.

An 129I Mössbauer spectroscopic study of iodine doped in poly(vinylpyridines)

The charge densities and the configurations of iodine doped in poly(2‐ and 4‐vinylpyridines) have been studied by using the Mossbauer effect of 129I at 16 K. The ’’outer complex’’ is first formed in the system of poly(2‐vinylpyridine) and iodine. The extent of the charge transfer is estimated to be 0.22 in the outer complex, which is nearly the same as pure pyridine. The iodine of the outer complex varies gradually to the tri‐iodide anion and then to the iodide anion by accepting electrons from the pyridine ring of the polymer. In the system of poly(4‐vinylpyridine) and iodine both the outer complex and the ’’inner complex’’ are first observed, and the iodine species in these complexes vary gradually to the I3− ion and finally to the I− ion in a similar manner as the system of poly(2‐vinylpyridine) and iodine. From the values of the Mossbauer parameters the charge or electron populations of the iodine species are calculated, and the arrangements of these species are discussed.

Mössbauer spectroscopic study on polyacetylene doped with iodine

Abstract The 129 I Mossbauer effect has been applied to polyacetylene films of cis -(CHI 0.23 ) x as prepared and cis -(CHI 0.20 ) x led under dynamic evacuation. It has been clarified that both films contain linear I − 5 and I − 3 with symmetric charge population and that the fraction of I − 3 increases after evacuation. The mechanism of electrical conductivity in iodine-doped polyacetylene has been discussed on the basis of the chemical form and the dynamic behavior of the anion species.

Reversible charge-transfer phase transition in [(n-C3H7)4N][FeIIFeIII(dto)3](dto = C2O2S2)

We have investigated the physical properties of [(n-C 3 H 7 ) 4 N][Fe II Fe III (dto) 3 ](dto = C 2 O 2 S 2 ) by means of 57 Fe Mossbauer spectroscopy, ESR, and magnetic susceptibility. From the analysis of 57 Fe Mossbauer spectra, we have discovered a new type of first order phase transition for the title complex at about 120 K, where the charge transfer transition between Fe II and Fe III occurs reversibly. Moreover, we have found the ferromagnetic phase transition at 6 K.

Crystal structure and anisotropy of iodine-intercalated Bi2Sr2Can−1CunOx

The electronic state and structural configuration of the intercalated iodine species in stage-1, I-Bi2Sr2Can−1CunOx (n = l, 2), have been studied through polarization-resolved Raman and129I Mössbauer spectroscopy. The polarization dependence of the Raman spectra and the Mössbauer measurement confirmed the dominant species to be triiodide ions, I3−, with alignment of these linear molecules either along thea- orb-axis in the host crystals. Transport measurements such as thermoelectric power and Hall coefficient clearly indicated that hole carriers are doped into the CuO2 planes upon intercalation, by whichTc of the host superconductor is changed. Furthermore, based on resistivity measurements in a magnetic field, we suggest that the iodine intercalation leads to a decrease of the anisotropy both in normal and superconducting states, suppressing the extremely two-dimensional character of the Bi2Sr2Can−1CunOx systems.

Light polarization in iodine-doped polyvinyl alcohol films

Abstract129I Mössbauer measurements have been performed on unidirectionally stretched iodinedoped polyvinyl alcohol(PVA) films which are widely used as optical polarizers. In the films iodine is observed to be in the form of I−, I3−, and I5− and the stretch of the films increases the abundance of the polyiodides, I3− and I5−. In the stretched PVA films, it has become clear that the linear polyiodides lie parallel to the stretching direction.

197Au Mössbauer study of Au/Ni artificial multilayers

Abstract197Au Mössbauer measurements have been performed at 16 K on the Au/Ni artificial multilayers having three different thickness of the layers those are 10Å Au/10Å Ni, 30Å Au/30Å Ni and 53Å Au/53Å Ni on a 250Å pure Au buffer layer. Mössbauer spectra obtained can be decomposed into mainly two components. One is an unperturbed component having an identical isomer shift value to the bulk Au metal. The other is the component perturbed strongly by the Ni layer indicating a broad contribution at positive velocity side and its intensity depends on the thickness of the Au layer. The spectrum from 10Å Au/10Å Ni multilayer is an entirely perturbed one and its area ratio to the component rising from pure Au buffer layer indicates the large Debye-Waller-factor suggesting the supermodulus effect in this multilayer.

Mössbauer study of fullerene C60 doped with 129I

Abstract The fullerene C 60 doped with iodine has been studied using 129 I Mossbauer effects at 16K. The six different species of doped iodine were observed in our measurements. The main species is a slightly positive-charged iodine. It is intercalated in the crystal part of the iodine-C 60 compound, and the state of the iodine is a molecular form (I 2 ). Therefore, the species of iodine exist in the fullerene as a weak electron donor and the amount of a total charge on the I 2 molecule is obtained to be +0.2. One of the other iodine species found in our Mossbauer study is I 2 molecule, which is physically adsorbed on the surface of C 60 polycrystals and is easily removed by a degas-treatment. The rest of the species is attributed to negative-charged iodine species. The amount of these negative-charged species tends to increase with the raise of the reaction temperature of iodine and C 60 . It was found that there is no relation between the amount of iodine with negative charges and the initial mixing ratio of iodine and C 60 .

Mössbauer study of iodine-doped polythiophene and poly(3-methylthiophene)

The129I Mössbauer study applied to the iodine-doped polythiophene and poly(3-methylthiophene) films revealed that the iodine consists of pentaiodide, triiodide, and/or I2 molecules. The abundance ratios of these iodine species vary with the doping level.

197Au Mössbauer spectroscopic study on the three-dimensional halogen bridged mixed valence complexes M2Au2X6 (M = K, Rb; X = Br, I)

Abstract M2Au2X6 (M = K, Rb; X = Br, I) are halogen bridged three-dimensional Au mixed valence complexes. We investigated the Au valence states in these complexes by means of 197Au Mossbauer spectroscopy, and discussed the charge transfer interaction between the AuI and AuIII ions.