Solvent Effects on the Photophysical Properties of Unexplored Imidazo[1,2‑a]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.