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

• Published in: ChemistrySelect (Weinheim) 2017-02, Vol.2 (5), p.1793-1801
• Main Authors: Deshapande, Narahari, Pujar, G. H., Sunagar, Manjunath G., Gaonkar, Supreet, Belavagi, Ningaraddi S., Inamdar, S. R., Bathula, Chinna, Khazi, Imtiyaz Ahmed M.
• Format: Article
• Language: English
• Subjects: Density Functional Theory; Intramolecular Charge Transfer; Oxadiazole; Photoluminescence; Quantum yield
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.201700048

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. A series of highly conjugated D‐π‐A chromophores containing 1,3,4‐oxadiazole were designed and synthesized. The compounds 3(a–g) emit intense blue‐green‐yellow fluorescence with better quantum yields and strong ICT character. The HOMO, LUMO and energy band gap values are in good agreement with the band gaps obtained from DFT and CV. The thermal and morphological stabilities of compounds were confirmed by DSC and TGA analysis and they are found to be stable at higher temperatures.