Dual-state emissive imidazo[1,2-α]pyridines with full color emission, acidochromism, viscosity-dependent fluorescence, and bioimaging applications

Five novel dual -state emissive imidazo[1,2-alpha]pyridine-based luminogens IP1-5 were rationally designed and prepared by varying the conjugation length and the nature of donor -acceptor (D -A) units. These D -A chromophores displayed cyan, green, yellow, and red fluorescence in the solid state, with full -color emission achieved for the first time through modification of imidazo[1,2-alpha]pyridine core. Interestingly, IP1 and IP5 in the solid state exhibited an abnormal remarkable blue -shift emission compared with those in THF, probably due to the highly twisted molecular conformations and solvent effect by theoretical calculations as well as crystal structure analyses. Importantly, IP1-5 revealed remarkable reversible acid -induced acidichromism, accompanied with dual change of colorimetric and fluorometric determination. Viscosity -dependent fluorescence was next conducted, indicting IP1-3 can be utilized for local viscosity detection. Moreover, IP1-5 served as promising candidates for multicolor bioimaging with low cell toxicity and good biocompatibility.