A highly efficient solution and solid state ESIPT fluorophore and its OLED application†
We present herein the synthesis and photophysics of 2,2′-bipyridine-3,3′-diol-5,5′-dicarboxylic acid ethyl ester (BP(OH)2DCEt2), an excited state intramolecular proton transfer (ESIPT)-based fluorophore featuring two identical intramolecular hydrogen bonds. BP(OH)2DCEt2 emits efficiently not only in solution, including protic solvents (λem = 521 nm, Φf = 40 to 75%), but also in crystalline state (λem = 530 nm, Φf = 51%). In addition, its saponified form (Na2BP(OH)2DC) is highly fluorescent in water (λem = 490 nm, Φf = 51%). Finally, the good electroluminescence performance of BP(OH)2DCEt2 is also demonstrated in an OLED device.