Solvent Effects on the Photophysical Properties of Unexplored Imidazo[1,2- <i>a</i> ]pyridine Derivatives

Simple imidazo[1,2-a]pyridine derivatives were synthesized via the GBB reaction, and their photophysical properties were studied for the first time. Fluorescence quantum yields confirmed a push–pull design, and absorption spectra showed a blue shift for bromo- and nitro-substituted derivatives at the ortho position (4b, 4d), whereas the cyano-substituted analogs at the para position (4f, 4p) exhibited a red shift. Solvent polarity significantly affected the fluorescence spectra, causing a red shift in polar solvents (4p, 4r) and a blue shift in nonpolar solvents (4i, 4m). A significant Stokes shift supported the involvement of an ICT mechanism in most cases. Some of the compounds demonstrated promising properties for use in fluorescent materials.