Synthesis and characterization of novel second-order NLO chromophores bearing pyrrole as an auxiliary electron donor

Abstract

Materials exhibiting large optical nonlinearities continue to be the subject of intense studies because of their potential application in modern communication technologies involving optical data processing, transmission, or storage, where they are gradually replacing classical electronic devices.Our recent studies have shown that replacing the benzene ring of a chromophore bridge with heterocycles (thiophene, pyrrole, thiazole), results in an enhanced molecular hyperpolarizability of conjugated donor–acceptor compounds. We were therefore motivated to explored the potential of donor-acceptor heterocyclic derivatives containing pyrrole as auxiliary electron donor linked to the thiazole heterocycle functionalized with strong acceptor groups. Compounds 1b-f were synthesized in good yields by Knoevenagel reaction between formyl derivative 1a and compounds bearing different electron-accepting groups. On the other hand precursor 1a was prepared through Paal-Knorr synthesis. In this communication we report on the synthesis, electrochemical properties, thermal stability and experimental determination of the second order nonlinear optical response (beta HRS = (199 – 408) x 10-30 esu) of these molecules which could be used as efficient and thermally stable NLO materials.