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

Abstract 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, T d  = 300 °C thus indicating its potential application as a second harmonic generation (SHG) chromophore.