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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