Abstract
A complex between α, α′-diphenyl-β-picrylhydrazyl(DPPH) and iodine is studied on the electrical conductivity, the magnetic susceptibility and the electron spin resonance. The optical absorption of the thin film of the complex shows that the absorption peak of iodine is observed at 400 mμ and the absorption peak at 530 mμ which is due to the unpaired electron of DPPH decreases with increasing iodine concentration. The ESR signal of the unpaired electron of DPPH also decreases with iodine concentration. Therefore, the unpaired electron of DPPH which is considered to contribute to electrical conduction plays an important role in forming the complex. By introducing iodine into DPPH single crystal as impurity the conductivity of DPPH increases up to as much as 103 of that of pure DPPH, and the activation energy becomes smaller than that of DPPH and is almost independent of iodine concentration. These phenomena are due to partially ionized DPPH which results from charge transfer structure.
The paramagnetic susceptibility of DPPH decreases linearly with increasing iodine concentration and this linearity breaks when the mole ratio of iodine to DPPH is two. From the results of susceptibility measurement, it is suggested that the electron which is transferred to iodine molecule is in diamagnetic state.
