Synthesis, characterization, and study of linear and non-linear optical properties of some newly thieno[2,3-b]thiophene analogs

Abstract New 3,4-diaminothieno[2,3-b]thiophene derivatives were synthesized by attaching with different aromatic have rich electron. The resulting compounds have been investigated by FT-IR, NMR, elemental analysis and optical absorption spectra. Comparison between the resulting compounds revealed that oxoindolin-3-ylidene)amino)thieno[2,3-b]thiophene has the highest absorption peak intensity at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:mo>∼</mml:mo> <mml:mstyle scriptlevel="0"/> <mml:mn>696</mml:mn> <mml:mrow> <mml:mtext>nm</mml:mtext> </mml:mrow> </mml:mrow> </mml:math> . Thin films have been prepared by thermal evaporation technique and characterized by UV-visible-NIR spectroscopy and the associated absorption, dielectric and dispersion parameters have been investigated and compared with other reported results. The obtained results indicated that diethyl 3,4-bis(((E)-2-oxoindolin-3-ylidene)amino)thieno[2,3-b]thiophene-2,5-dicarboxylate and 3,4-bis(((E)-2-oxoindolin-3-ylidene)amino)thieno[2,3-b]thiophene-2,5-dicarbonitrile have manifested small band energy gap energy 1.95 eV and 1.66 eV, respectively, as a result of increasing conjugation and high absorption coefficient, making these compounds ideal for use in solar cells. The high nonlinear parameters such as refractive index and third-order nonlinear susceptibility of these organic compound thin films are significantly asymptotic compared to chalcogenide and oxide materials, making them suitable for nonlinear optical devices.