Effect of substitution group on dielectric properties of 4H-pyrano [3, 2-c] quinoline derivatives thin films

The AC electrical conductivity and dielectrical properties of 2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-
dihydro-4H-pyrano[3, 2-c]quinoline-3-carbonitrile (Ph-HPQ) and 2-amino-4-(2-chlorophenyl)-6-ethyl-5-oxo-5,6-dihydro-
4H-pyrano [3, 2-c] quinoline-3-carbonitrile (Ch-HPQ) thin films were determined in the frequency range of 0.5 kHz–5 MHz
and the temperature range of 290–443 K. The AC electrical conduction of both compounds in thin film form is governed
by the correlated barrier hopping (CBH) mechanism. Some parameters such as the barrier height, the maximum barrier
height, the density of charges, and the hopping distance were determined as functions of temperature and frequency. The
phenoxyphenyl group has a greater influence on those parameters than the chlorophenyl group. The AC activation energies
were determined at different frequencies and temperatures. The dielectric behaviors of Ph-HPQ and Ch-HPQ were investigated
using the impedance spectroscopy technique. The impedance data are presented in Nyquist diagrams for different
temperatures. The Ch-HPQ films have higher impedance than the Ph-HPQ films. The real dielectric constant and dielectric
loss show a remarkable dependence on the frequency and temperature. The Ph-HPQ has higher dielectric constants than
the Ch-HPQ.