Near Attack Conformation as Strategy for ESIPT Modulation for White-Light Generation

Abstract

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 1H NMR. Organic Light-emitting Diodes (OLEDs) were ensembled as Al/Ca/PVK:X/PEDOT: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.