Electrical Properties and Constitution of the Phenothiazine–Iodine and Related Complexes

The electrical properties of the phenothiazine–iodine complex were examined in detail as a function of the composition. A shoulder in the resistivity-composition isotherm, a decrease in the activation energy for semiconduction by a factor of two, and a change in the sign of the Seebeck coefficient from negative to positive were observed at a composition of two molecules of phenothiazine to five atoms of iodine. These observations and the spectral behavior reported earlier indicate the formation of a complex cation radical salt, (phenothiazine)2+I5−, which exhibits a resistivity of about 800 ohm cm at room temperature. By the incorporation of a half mole of iodine into this salt, the resistivity reaches a minimum of about 20 ohm cm at room temperature. Similar singularities in the resistivity-composition isotherms were observed with the complexes of the benzo[a]-, benzo[c]-, and N-methylderivatives.