Constructing fused bis-isatins from pyrroloindoles using direct oxidation approach and re-visiting indophenine reaction. (1st December 2020)

• Record Type: Journal Article
• Authors: Bhanvadia, Viraj J.; Choudhury, Anwesha; Iyer, Parameswar Krishnan; Zade, Sanjio S.; Patel, Arun L.
• Is Part Of: Polymer. Volume 210(2020)
• Publication Date: 2020-12-01
• Subjects: Conjugated polymers -- Donor-acceptor systems -- Electron-deficient compounds -- Fused ring systems -- Oxidation -- Polymerization; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2020.123032
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Two novel electron accepting bis-isatins, having fused bis-lactam rings have been synthesized from corresponding pyrroloindoles 7 and 14 by one-pot direct oxidation approach involving oxidant NBS with or without co-oxidant TBHP in DMF/CHCl3 . Synthesized fused bis-isatins 8 and 15 are extensively studied for thermal, photophysical, electrochemical and thin-film morphological properties and are found to have characteristic properties like solid-solid transitions, visible light absorption, lowered FMO energy levels (LUMOs below −4.1 eV and HOMOs below −5.9 eV) as well as oriented packing of molecules in the film state. The famous indophenine reaction is re-visited with fused bis-isatins to form conjugated polymers P-1 and P-2, having quinoidal pyrroloindole dione units. The polymers are studied for thermal, photophysical, electrochemical and thin-film morphological properties indicating sufficiently high thermal stability (up to 200 °C), extended absorptions up to near IR region, lowered FMO energy levels (LUMOs below −4.3 eV and HOMOs below −5.8 eV) and amorphous nature of polymer films. Graphical abstract: Image 1 Highlights: Pyrroloindoles (Electron donors) converted into fused bis-isatins (Electron acceptors). Direct oxidation approach, room temperature reactions without transition metals. Quinoidal conjugated polymers developed by Indophenine reaction of fused bis-isatins. Intense low energy absorptions from HOMO-LUMO charge transfer transitions. Ambipolar redox behaviour with much lowered frontier energy levels.