CuO–CuAl2O4 and d-glucose catalyzed synthesis of a family of excited state intramolecular proton transfer imidazo[1, 2-a]pyridine analogues and their optical properties. (October 2015)

• Record Type: Journal Article
• Authors: Balijapalli, Umamahesh; Iyer, Sathiyanarayanan Kulathu
• Is Part Of: Dyes and pigments. Volume 121(2015)
• Page Start: 88
• Page End: 98
• Publication Date: 2015-10
• Subjects: Imidazo[1, 2-a]pyridine -- Tandem process -- ESIPT emission -- Solid-state emission -- Solvatochromism -- Electroluminescence; Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2015.05.014
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: A simple and efficient route to luminescent imidazo[1, 2- a ]pyridines from 2-aminopyridines, phenylacetylene and arylaldehydes was achieved by an one-pot, tandem process starting with an A3-coupling followed by 5-exo-dig cyclization. Copper(II)oxide/copper aluminate composite (5 wt% CuO–CuAl2 O4 composite) andd -glucose catalyzed optimal conditions for the reaction were established after examining various reaction parameters such as solvent, catalyst and temperature. The synthesis was much compatible with various functionalities. 2-Aryl-imidazo[1, 2- a ]pyridines not capable of excited state intramolecular proton transfer emission displayed moderate fluorescence quantum yields in the blue-green region due to intramolecular charge transfer process. In addition, they exhibited peculiar solvatochromic behaviour in chlorinated solvents like chloroform and dichloromethane. Products containing 2-(2′-hydroxyphenyl) substituent underwent excited state intramolecular proton transfer in non polar and polar-aprotic solvents. Although such type of emission in solvents was very weak, the Stokes shifts values were high (14, 638–11, 448 cm −1 ) with strong solid-state emission in green to yellow region. Graphical abstract: Highlights: CuO–CuAl2 O4 composite andd -glucose catalyzed A3-coupling was developed. 2-Aryl-imidazo[1, 2- a ]pyridines displayed peculiar solvatochromic behaviour in chlorinated solvents. 2-(2′-Hydroxyphenyl) substituent underwent ESIPT process in non polar and polar solvents. Solid state ESIPT is desired factor for solid state lightening materials like OLEDs and lasers.