Simple imidazo1,2-apyridine 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.
Praciano et al. (Fri,) studied this question.