Synthesis, thermal behavior and optical characterizations of thin films of a novel thiazole azo dye and its copper complexes.

In the present paper, a novel dye of 4-methyl-5-(4-acetylphenyldiazenyl)thiazol-2-amine (L) and its corresponding copper complexes are synthesized and characterized using different techniques including elemental analysis, thermal analysis, 1H NMR, Mass, and FT-IR spectra. The thermal behavior of L and its complexes is carried out and discussed using thermogravimetric analysis, and it observed that the type of copper substituent affects the thermal decomposition of complexes. Homogenous thin films of L and its complexes are successfully grown onto quartz substrates using spin coating technique. Optical features and spectral phenomena of the thin films are studied using spectrophotometric measurements of absorbance, transmittance and reflectance. The optical constants such as refractive index, extinction coefficient, optical conductivity and energy loss functions of the thin films of L and its complexes are calculated. The refractive index curves for all films show a normal dispersion behavior in the non-absorbing region of spectra, from which the dispersion parameters can be calculated using Wemple-DiDomenico model. The type of optical transition bands shows indirect allowed. The values of the optical energy gap are calculated in the range from 2.13 to 2.33 eV, depending on the nature of Cu(II) substituent. Indeed, the present results show that the complexes as organic semiconductors acquired good characterizations better than metal free ligand (L) such as more thermal stability, reducing in the optical band gap and increasing in the absorption coefficient that refers to light harvesting capacity.