Geometrical structures, thermal, optical and electrical properties of azo quinoline derivatives

Azo quinoline derivatives (AQx) were synthesized by coupling of 8-hydroxyquinoline with aniline derivatives. The optimized bond lengths, bond angles and the quantum chemical parameters for the ligands (AQx) were calculated. The dielectric constants (εr and εi) and ac conductivity (σac) were studied as a function of both temperature and frequency in the temperature range 293-509 K and frequency range 102-105 Hz. The thermal activation energies ΔE1 and ΔE2 were calculated and found to be in the range of 0.03-0.26 and 0.2-1.31 eV, respectively, depending on the substituent and frequency. The conduction mechanism was investigated for all the derivatives under investigation. The ligands (AQ1, AQ2 and AQ4) were found to be controlled by correlated barrier hopping model and the ligands (AQ3 and AQ5) were controlled by small polaron tunneling mechanism. The optical absorption properties of the ligands thin films were investigated. The absorption coefficient (α) spectra reveals two absorption peaks which are assigned as π-π⁎ and n-π⁎ transitions. The optical energy gap (Eg) was investigated near the absorption edge and found to be in the range of 1.34-2.26 and 1.47-1.69 eV for direct and indirect optical transitions, respectively.