Excimer-like emission from linear π-conjugated poly(pyridine-2,5-diyl)

π-Conjugated poly(pyridine-2,5-diyl) and poly(2,2′-bipyridine-5,5′-diyl) give rise to fluorescence in formic acid solutions, in the solid state (film), and in an adduct with poly(vinyl alcohol); the fluorescence in the solid state, in the adduct with poly(vinyl alcohol), and in the formic acid solution with relatively high concentration of the polymer is interpreted by assuming excimer formation.