LAUSR

Abstract Three novel positional isomers, namely (E)-3-(2-chloroimidazo[1,2-a] pyridin-3-yl)- 1-(pyridin-2-yl)prop-2-en-1-one (1), (E)-3-(2-chloroimidazo[1,2-a]pyridin-3-yl)-1- (pyridin-3-yl)prop-2-en-1-one (2) and (E)-3-(2-chloroimidazo[1,2-a]pyridin-3-yl)- 1-(pyridin-4-yl)prop-2-en-1-one (3), were obtained through a mild approach. Powder X-ray diffraction patterns demonstrate their various stacking structures, attributed to positional isomeric effects. Furthermore, these positional isomers exhibit different phosphorescent colors and quantum yields. Interestingly, these positional isomers also reveal reversible phosphorescent color switching in the response to acid-base vapor stimuli. The present work provides a promising approach for synthesizing organic materials and a new access to develop dynamic functional materials which can be reversibly switched between different phosphorescence based on external acid-base vapor stimuli.