Synthesis and Optoelectronic Exploration of Highly Conjugated 1,3,4-Oxadiazole Containing Donor-π-Acceptor Chromophores

Abstract

A series of novel highly conjugated Donor-π-Acceptor (D-π-A) chromophores 3(a-g) are designed and synthesized through the Wittig Reaction. These molecules contain an aryl/heteroaryl groups as an electron donor (D) and electron transporting oxadiazole as acceptor (A). The structural integrity of the compounds was characterized by 1H NMR, 13C NMR and GC-MS analysis. The photophysical properties have been studied in detail using UV-Vis absorption, fluorescence spectroscopy and time-resolved fluorescence measurements. These synthesized compounds emit intense blue-green-yellow fluorescence with reasonably good quantum yields. In addition, steady-state absorption and fluorescence measurements were carried out in solvents of varying polarities to understand the intramolecular charge-transfer (ICT) characters of these compounds. The solvent dependency of the large Stokes shifts and high dipole moment of excited state also supported the charge-transfer character of the excited state. The combined experimental Cyclic Voltammetry (CV) and theoretical methods (DFT) were performed to investigate structure-property relationship and ICT property of these compounds. The computed values were found to be in good agreement with the experimental results. The results demonstrated that the novel D-π-A chromophores could play important role in organic optoelectronics.