Push–pull second harmonic generation chromophores bearing pyrrole and thiazole heterocycles functionalized with several acceptor moieties: Syntheses and characterization

• Synthesis of heterocycles using commercially available precursors and simple experimental procedures.
• The optical properties (linear and nonlinear) of the new compounds were investigated.
• The thermal stability of the chromophores was studied by thermogravimetric analysis.
• The indanone derivative exhibits the large first hyperpolarizability and the higher thermal stability.
• Novel pyrrolyl-thiazole based push–pull heterocyclic systems for nonlinear optical applications.

A new series of push–pull nonlinear optical (NLO) chromophores 2 and 3 were synthesized in order to study the variations produced in the optical properties of the compounds by linking different electron accepting moieties to the pyrrolyl-thiazole system at position 5 of the electron deficient thiazole heterocycle. The final donor–acceptor systems 3a–c were synthesized by a modification of the Paal–Knorr synthesis (the Clauson-Kaas reaction) followed by Knoevenagel reaction of the precursor aldehydes 2a–c with active methylene molecules. Hyper-Rayleigh scattering in dioxane solutions using a fundamental wavelength of 1064 nm was employed to evaluate their second-order nonlinear optical properties. An indanone dicyanovinyl derivative 3c exhibited the largest first hyperpolarizability (β = 970 × 10−30 esu, using the T convention) as well the highest value of decomposition, Td = 300 °C thus indicating its potential application as a second harmonic generation (SHG) chromophore.

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