Hydroxy-benzimidazoles as blue-green emitters: Synthesis, structural and DFT studies

Sathyanarayana, Reshma and Kumar, Vasantha and Pujar, G. H. and Poojary, Boja and Shankar, Madan Kumar and Yallappa, Sangappa (2020) Hydroxy-benzimidazoles as blue-green emitters: Synthesis, structural and DFT studies. Journal of Photochemistry and Photobiology A - Chemistry, 401. ISSN 1010-6030

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The new benzimidazole ligands (3a-e) were synthesized using ethyl 4-(butylamino)-3-nitrobenzoate and substituted salicylaldehyde in the presence of sodium dithionite reagent which undergoes ``one-pot'' nitro reductive cyclization. Here benzimidazole moiety acts as an electron-acceptor (A) whereas substituted 2-hydroxyphenyl moiety acts as an electron-donor (D) unit. The molecular structures were characterised by FTIR, H-1 NMR, C-13 NMR, single crystal XRD and MS analysis. Optoelectronic properties were determined by UV-vis, solution and solid photoluminescence, quantum yield and lifetime. The solvent-dependent absorption and emission were studied using both polar protic and polar aprotic solvents. All the derivatives exhibited ESIPT, especially compound ethyl 1-butyl-2-(3,5-dichloro-2-hydroxyphenyl)-1H-benzod]imidazole-5-carbox ylate (3e) displayed dual emission in both polar protic and polar aprotic solvents. The compound stability and electrochemical property were determined by thermal gravimetric analysis (TGA) and cyclic voltammetry (CV) respectively. The compounds emit intense blue-green fluorescence with high to moderate quantum yield. Also, these derivatives exhibited a high Stokes shift. The computational studies like Density-Functional Theory (DFT) and Molecular Electrostatic Potential (MEP) were conducted to provide important insights into the structure-property relationships. The crystal packing is stabilized through intermolecular hydrogen bonds (C-H center dot center dot center dot O) and intermolecular interactions (pi center dot center dot center dot pi). The findings of results help in developing novel ligands in the field of organic optoelectronics.

Item Type: Article
Uncontrolled Keywords: Benzimidazole; Photoluminescence; DFT; Cyclic voltammetry; MEP; Quantum yield; Fluorescence lifetime; ESIPT
Subjects: C Chemical Science > Chemistry
Divisions: Department of > Institution of Excellence
Depositing User: Mr Umendra uom
Date Deposited: 09 Mar 2021 09:30
Last Modified: 09 Mar 2021 09:30
URI: http://eprints.uni-mysore.ac.in/id/eprint/15504

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