Yasuo Deguchi

ESR studies of electrochemically prepared poly(3-methylthienylene) films

Abstract ESR measurements have been performed on samples of poly(3-methylthienylene, poly(3-methylthienylene) perchlorate, and poly(3-methylthienylene) iodide. The ESR lines observed are concluded to come from defects in the π-conjugated system. It is deduced that the current carriers in the doped film are spinless and the role of bipolarons in the conduction mechanism is suggested.

Magnetic Properties of Organic Stable Radicals. I. 2,2,6,6-Tetramethyl-4-Hydroxypiperidine-1-Oxyl

The static magnetic susceptibility and the ESR absorption spectra of 2,2,6,6-tetramethy1-4-hydroxypiperidine-1-oxyl in the temperature range from 1.8°K to 300°K have been measured. This powder sample shows a broad maximum in the susceptibility at the temperature 6.5°K. It has been shown that the temperature dependence of the susceptibility is fitted better by the one-dimensional Heisenberg model than the linear Ising model or a singlet-triplet model. The Curie-Weiss constant and the exchange interaction energy along the chain are estimated to be -6.0°K and -5.0°K, respectively. The linewidth of the ESR absorption spectra increases rapidly as decreasing temperature below 6.5°K.

Weak association between alkali metal ions and mononegative ions of aromatic hydrocarbons

Extra hyperfine splittings due to alkali metalal cations have been observed in the electron spin resonance (E.S.R.) spectra of biphenyl, naphthalene, anthracene and pyrene mononegative ions. It is interpreted as being due to ion-pair association between the aromatic anions and the metal cations. The unpaired spin densities at the metal nuclei are estimated using the data from the atomic beam experiments. In the case of biphenyl-alkali metal systems the appropriateness of the model described in a previous paper has been checked by studying the temperature dependence of the cation hyperfine splittings and the E.S.R. spectra of some methyl substituted biphenyl anions. The structure of the ion-pairs are discussed using Mullikens theory of charge-transfer complexes.

Magnetic Phase Transition of Organic Free Radical p-Cl-BDPA

The heat capacity of polycrystalline organic free radical, p -Cl-BDPA, has been measured between 1.5 and 20 K. The broad maximum near 5 K in the magnetic heat capacity corresponds the short range magnetic ordering of the unpaired electron. At 3.25 K a sharp peak was observed, which indicates paramagnetic-antiferromagnetic phase transition. The magnetic entropy of this transition yields 101.5% of the expected Rln2. Below T N the magnetic heat capacity was in good agreement with the three-dimensional spin wave theory of antiferromagnet.

ESR studies of the anomalous phase transition in crystalline galvinoxyl radical

The ESR spectra of powder samples of pure galvinoxyl and 1% galvinoxyl diluted in phenol matrix is measured in the temperature range 77–293 K.(AIP)

ESR studies of polycondensate of fused Polynuclear aromatics (COPNA) resin with ferromagnetic behaviour

Abstract ESR measurements have been performed on the samples of the title compounds with ferromagnetic behaviour. It is deduced that the corresponding spins are of π-type, the concentration of which is very small. A possibility of the delocalization of the spins in the resin skeleton is suggested.

ESR studies of polyacenic semiconductive material

Abstract ESR measurements have been performed on the polyacenic material prepared by the pyrolytic treatment of phenol-formaldehyde resin. Six kinds of samples (A)-(F) with various electrical conductivity (σ) were employed for the measurements. Each sample shows a single narrow line, the g -values of which suggest the existence of unpaired electrons of π-type. If the sample (F) ( σ = 1 × 10° S cm −1 ) the single narrow line becomes drastically diminished in the presence of a small amount of oxygen.

ESR study for the oxidation of pyrrole in the presence of a spin trap

Abstract We have studied electron spin resonance (ESR) spectroscopy during the oxidation of pyrrole and its derivatives in the presence of spin traps in order to clarify the polymerization mechanism of pyrrole. When pyrrole monomer was chemically oxidized in the solution containing nitrosobenzene, the paramagnetic species (the ESR spectrum of which is assigned to C 6 H 5 NHO . ) was detected. No direct trapping of the pyrrole σ-radical strongly suggests that the polymerization of pyrrole progresses not through the neutral σ-radical but through the cationic π-radical of the monomer.

ESR study of in situ doped polyacenic semiconductive material with iodine and bromine

Abstract Polyacenic semiconductive materials prepared by heat treatment (835 and 1020 °C) of phenol-formaldehyde resin can be doped with I 2 and Br 2 . The ESR spectra of such doped materials have been obtained by both ordinary measurement and in situ doping technique. The Br 2 -doped samples also show a broad line shape like the I 2 -doped samples. The values of peak-to-peak line width (ΔH pp ) in the Br 2 -doped samples are smaller than those of the I 2 -doped samples. Moreover, in the ESR measurements of these samples during in situ doping with these dopants, it has been found that the sharp and narrow peak changes continuously broader with decrease of signal intensity. To investigate whether the change of line shape is reversible or not, chemical compensation has been performed on these doped samples with ammonia water.

A study on the semiconductive materials prepared by pyrolytic treatment of organic resins

Abstract A comparative study of semiconductive materials prepared by pyrolytic treatment of several kinds of organic resins in the range 540 to 860 °C has been performed. X-ray diffraction and electron spin resonance measurements, etc. for these materials have been attempted so as to obtain information on their structural and property differences. The results of the analyses have shown that the structures of these materials strongly depend upon those of the original resins. A preliminary doping check has revealed that the hardly graphitizing material such as that prepared from the phenol-formaldehyde resin shows the highest efficiency.