Multicomponent one-pot synthesis of luminescent imidazo [1,2-a]pyridine-3-amines. Studies of fluorescence, solvatochromism, TD-DFT calculations and bioimaging application

Abstract

Herein we report on a novel series (4a-4p) of fluorescent Imidazo [1,2-a]pyridines (IMPs) synthesized via an eco-friendly microwave-assisted Groebke-Blackburn-Bienaymé reaction (GBBR), in good to excellent yields (80–92%) and under a green catalyst. The target molecules absorb at the UV–vis region and emit from blue- to greenish fluorescence with relatively large Stokes shifts (6780–9011 cm−1) due to an Intramolecular Charge Transfer (ICT) process from the strong donor triphenylamine (TPA) to the acceptor Imidazo [1,2-a]pyridine. Time dependent DFT calculations were performed to interpret the structure–property relationships and corroborate the ICT character and assess their energy band gaps. In addition, imaging studies of the HEK293 and HeLa cell lines revealed that the IMP 4e, with the highest quantum yield of fluorescence (φfl) of 66%, is a specific blue fluorescent probe to stain the DNA of the nucleus.