D-A-π-D Synthetic approach for thienyl chalcones – NLO – a structure activity study

Abstract

With the growing interest for organic molecules in Nonlinear Optical (NLO) applications, we have synthesized nine novel thienyl chalcones based on the D-A-π-D design. In order to establish the identity, these have been characterized in detail. Having followed the design based synthetic route, we have focused on two prime criteria for comparison; namely second harmonic generation (SHG) and non-linear absorption. In this work the role of the electron withdrawing groups, electron donating groups and extended conjugation, have been extensively studied vis-à-vis the NLO properties. The change in these properties by virtue of the molecular structure has been elucidated in this work as the structure activity relationship. Optical nonlinearity is studied using ultrafast (100 fs) laser pulses at 800 nm, employing the open aperture Z-scan technique. The compounds exhibit large effective three-photon absorption (3PA) coefficients, in the order of 10−28 m3/W2. These observations show that these compounds possess potential for application in all-optical limiting and switching devices.