Electronic Properties of Benzidine·TCNQ System

Publisher Website
Google Scholar
Abstract
The benzidine·tetracyano-p-quinodimethane (TCNQ) system forms two types of charge-transfer complexes; one (I) containes some sort of solvent molecules, while the other (II) does not. The electronic properties of I have been found to be unusual in many respects compared to II which shows the properties expected from those of ordinary charge-transfer complexes. I and II did not exhibit ESR absorption, if they were well-grown crystals. However, when they were pulverized to fine powder, I showed a strong absorption while II did not. The visible range absorption spectra of I and II consisted of three main bands, but all the bands of I were found to be shifted to longer wavelengths compared to those of II. In addition to these bands, two shoulders were found in the spectrum of I. The shoulders were considered to be due to the ion radicals produced from benzidine and TCNQ. The electrical resistivities are again quite different from one another. The resistivity of I was found to be 103–105 ohm cm at room temperature, the value being dependent on the kind of the solvent molecules included, while that of II was 2×109 ohm cm. The activation energy for conduction was smaller for I (0.1–0.2 eV) than for II (0.34 eV).