Temperature-sensitive protonic-dipole mediated conduction in hexa-azophenol derivative of cyclotriphosphazatriene

Extending the range of molecular mesomerism, at the expense of ion mobility, in the cyclotriphosphazatriene ring across azo linkages to hexa phenolic rings yields dielectric features that are challenging. At low temperature, the electric permittivity shows low frequency dispersion. The dielectric loss changes this frequency dependence upon approaching 500 K due to the propagating contribution from a polarization-induced dc conduction, which assists in merging the slope of that dependence above 10 kHz within the much higher value slope at lower frequencies. The dielectric loss also rises with temperature while concurrently the relaxation energy drops; both electric features show a critical break at 500 K. The electric impedance exhibits a Cole–Cole semicircle Z″–Z′ dependence above 500 K indicative of ionic relaxation. Z″–Z′ tends to a perturbed linear dependence at lower temperatures due to an increasing disturbance of the ionic conduction by dipole interaction of higher relaxation energy. These results are ascribed to the phenolic protons of the azophenol derivative, which are highly associated at low temperatures so that they conduct via high relaxation energy dipole interactions. Thermal treatment mobilizes the strongly associated phenolic protons so that a more protonic conduction of 2–3 orders higher conductivity is developed with a much lower relaxation energy above 500 K. These findings are supported at the molecular level by varying temperature solid state FTIR spectroscopy.