Substituent Effects on the Electrical Conductivities of the Phenazine Derivatives

Abstract

The dark and/or photoconductivities of 16 substituted phenazines having methoxy, hydroxy, chloro, nitro, amino or t-butyl group at 1-, 2-, 1, 6- or 2, 7-positions of the phenazine ring have been investigated by using the surface-type and/or sandwich-type, cells. As shown in Table 1, the resistivities at 20 C (p20) were higher than 10 14 ohm-cm. The energy. gaps ( e )of the dark conductivities in the range from 2.0 to 2.3 eV were independent of the kinds and the positions of the substituents, although the longest wavelength band in the visible absorption spectra of the evaporated films changed With them. The photocurrent became larger by ihtroducing the substituents at 1, 6-pbsitions of the phenazine ring, the photocurrents of the 1, 6-disubstituted phenazines were 10 - 10 3 times larger than those of the other substituted phenazines, as shown in Table 4. When the substituent at 1, 6-positions was hydroxy or amino group, however, the photocurrents were not detected. The photocurrents of all phenazines decreased in oxygen, although that of anthracene increased. No correlation between the photoconductivity and fluorescence was observed. Furthermore, the spectral properties of the 1, 6-disubstituted phenazines were compared with those of the 2, 7-disubstituted phenazines, it was deduced that the t-butyl groups at 1, 6-positions adjacent to the lone-pair electrons of the nitrogen atoms of the phenazine ring interfered with the protonation of the lone-pair electrons with acetic acid.