New proton transfer lasing systems—derivatives of 2,2′-bipyridyl. Synthesis and photophysical characteristics

Abstract Two new bipyridyl derivatives undergoing the excited state intramolecular proton transfer were synthesized: 5-methyl-[2,2′-bipyridine]-3,3′-diol and 5,5′-dimethyl-[2,2′-bipyridine]-3,3′-diol. Both reveal a strong phototautomeric, largely Stokes-shifted fluorescence and can be used as proton transfer laser dyes. Tuning ranges and lasing efficiences are also reported.