Synthesis, characterization, and DFT study of linear and non-linear optical properties of some novel thieno[2,3-b]thiophene azo dye derivatives

Abstract

Some novel thieno[2,3-b]thiophene-2,5-dicarbonitrile derivatives namely; 3,4-bis(2-hydroxynaphthalen-1-yl)diazenyl)thieno[2,3-b]thiophene-2,5-dicarbonitrile, 3,4-bis(4-aminonaphthalen-1-yl)diazenyl)thieno[2,3-b]thiophene-2,5-dicarbonitrile and 3,4-bis(4-(dimethylamino)phenyl) diazenyl)thieno[2,3-b]thiophene-2,5-dicarbonitrile have been synthesized and characterized by FT-IR and NMR spectroscopies.Thin films of the synthesized thieno[2,3-b]thiophene-2,5-dicarbonitrile derivatives have been deposited by the thermal evaporation method and characterized by UV-VIS-NIR spectroscopy. Their spectral dependences of absorption, dielectric, dispersion and allied parameters have been investigated, discussed, and compared with published results. The high absorption coefficient (∼105cm−1) at a solar maximum wavelength (λ≅500nm) and the band and optical gap energies of 2.95 and 2.15 eV, respectively manifested by the present samples make them suitable to be applied in optoelectronic devices, especially as solar absorber material. The revealed high values of non-linear refractive index n2 and 3rd order non-linear susceptibility revealed by these organic compound films, which are significantly higher than those of chalcogenide and oxide materials recommend them as promising NLO-elements. These results have been insured by geometry optimization and NLO calculations using Density Functional Theory with B3LYP method in the level of 6–311 G (d,p).