investigation on photophysical and third–order nonlinear optical properties of novel thermally–stable thiophene–imidazo [2,1-b][1,3,4] thiadiazole based azomethines

Abstract

The use of π–conjugated semiconducting materials in flexible and large–area optoelectronic devices is proliferated worldwide owing to the easy structural modifications and solution processability possible, leading to the change in opto–electronic properties. In this context, new class of thiophene and imidazo [2,1-b][1,3,4] thiadiazole (ITD) based conjugated azomethines (TI1–TI3) were designed and synthesized. The photophysical and electrochemical properties of the synthesized azomethines (TI1–TI3) were investigated experimentally, which were further validated with the aid of theoretical calculations. Further, the azomethines TI1 and TI2 were subjected to Z–scan analysis to study the nonlinear optical (NLO) properties. The molecules exhibited effective two photon absorption (TPA) with the large nonlinear absorption coefficient (βeff) of the order of 10−10 m W−1. The planar structure of TI1 furnished a better interaction between donor and acceptor moieties and extended the π–conjugation, providing an improved βeff (0.81 × 10−10 m W−1) to TI1 compared to that of TI2 (0.55 × 10−10 m W−1). From the results it is inferred that the molecules could be of potential materials to be used in efficient photonic devices.