Two derivatives salicylidene-4,6-(dimethylamino)pyridine (KM1) and salicylidene-5-bromo-4,6-(dimethylamino)pyridine (KM2) reactive to excited-state intramolecular proton transfer (ESIPT) were synthesized as a strategy to produce white light diodes with small organic molecules. White color resulted from the presence of both normal (420 nm) and tautomeric (550− 580 nm) species emission. The photophysical features of N* and T* were unveiled in solution and the solid state. The ESIPT mechanism revealed the influence of near attack conformation (NAC), and the relevance intramolecular hydrogen bonding (IMHB) further evaluated by 1 H NMR. Organic Light-emitting Diodes (OLEDs) were ensembled as Al/Ca/PVK:X/PE-DOT:PSS/ITO/glass where X = KM1 or KM2 (0.3% mol mol −1 ) using solution-processed protocols. KM1 or KM2 was solubilized in poly(9-vinylcarbazole), PVK, and the device of KM2 produced a chromaticity of (0.32, 0.27) according to the Commission Internationale de L'Eclairage (CIE) 1931 scale, which is slightly violet. The same device using KM1 reached CIE (0.33, 0.34), which is considered extremely close to pure white.
This work describes the photophysical properties of new salicylidene derivatives which undergoes excited state intramolecular proton transfer (ESIPT) and the role of solvent polarity and specific interactions with the dyes. These observations were obtained by steady-state and time-resolved electronic absorption and fluorescence techniques. Salicylidene derivatives were synthetized by Schiff’s condensation using an acid catalyst and they were characterized successfully by 1H and 13C NMR, FT-IR, HRTOF-MS and single-crystal X-ray diffraction and they photophysical properties were studied by the addition of a bromide moiety of the aromatic amine ring.
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