A highly efficient solution and solid state ESIPT fluorophore and its OLED application

Abstract

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 (λ_em = 521 nm, Φ_f = 40 to 75%), but also in crystalline state (λ_em = 530 nm, Φ_f = 51%). In addition, its saponified form (Na₂BP(OH)₂DC) is highly fluorescent in water (λ_em = 490 nm, Φ_f = 51%). Finally, the good electroluminescence performance of BP(OH)₂DCEt₂ is also demonstrated in an OLED device.