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 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.

Synthesis, photophysics, and theoretical calculations of styryl-based fluorophores harboring substituted benzothiazole acceptors

“…On the other hand, compound F2 showed a redshifted absorption maximum (398 nm) compared to previous compounds. This observation is due to the electronegativity of the halogen-atom, as already reported in the literature [37,38]. Indeed, theoretical calculations (see Section 3.3) indicated a charge transfer character from the amino moiety towards the aromatic frames, an effect magnified by the bromine substituent in F2 in comparison to F3.…”

Excited-State Intramolecular Proton Transfer: A Short Introductory Review

“…Probe molecules in various biological systems, based on this mechanism, have also been suggested recently [ 10 , 11 ]. Moreover, ESIPT systems have found applicability in sensors for humidity [ 12 , 13 ], luminescent solar collectors [ 14 ], proton transfer lasers [ 15 , 16 , 17 , 18 , 19 ], photo stabilizers [ 20 ], devices based on thermally activated delayed fluorescence [ 21 , 22 ], white light generation [ 23 , 24 , 25 ], organic light-emitting diodes (WOLED) [ 26 ] as well as suitability in sensing of anion and cations [ 27 , 28 , 29 , 30 ], photochromic switching [ 31 , 32 ] and even understanding of fading of colorants in art [ 33 ].…”

All-Solution Processed Single-Layer WOLEDs Using [Pt(salicylidenes)] as Guests in a PFO Matrix

“…Furthermore, different strategies are used to assemble organic LED devices with white emissions (WOLEDs) [ 13 ], which may include complex molecules with multiple chromophores [ 14 , 15 ], hybrid materials [ 13 ], excited-state intramolecular proton transfer (ESIPT) compounds [ 16 , 17 , 18 ], polymer blends with conjugated polymers [ 19 , 20 ], diodes with external color conversion layers (CCLs) [ 21 , 22 ], diodes with multilayers [ 23 , 24 ], thermally activated delayed fluorescent molecules [ 25 , 26 ], diode arrays with microlenses [ 27 ], nanocrystal/conducting polymer composites [ 28 , 29 , 30 ], and exciplex emitters [ 31 ]. The opportunities for innovation are truly huge.…”