Heteroaryl‐Substituted Bis‐Anils: Aggregation‐Induced Emission (AIE) Derivatives with Tunable ESIPT Emission Color and pH Sensitivity

Abstract

The two‐step synthesis, structural, and photophysical properties of a series of heteroaryl‐substituted bis‐anil derivatives presenting aggregation‐induced emission (AIE) coupled with an excited‐state intramolecular proton transfer (ESIPT) process is described. The fluorescence color of the aggregates can be fine tuned by changing the electronic nature of the peripheral substitution, leading to a wide range of emission wavelengths (from green to the near infra‐red). Moreover, upon introduction of strong electron‐withdrawing groups such as cyano (CN), a competition between ESIPT and deprotonation is observed leading to the emission of the anionic species at low water percentage. This observation led to the synthesis of an additional mixed AIE fluorophore, functionalized by methoxy groups on one side and cyano groups on the other side. Upon addition of water, this dye displays first anionic emission, followed by typical AIE/ESIPT red fluorescence upon formation of the aggregates. TD‐DFT calculations on selected AIE dyes were performed to rationalize the nature of the emissive transitions in these derivatives.

Solid-state emitters presenting a modular excited-state proton transfer (ESIPT) process: recent advances in dual-state emission and lasing applications

“…In a similar fashion, aggregation-induced emission (AIE) corresponds to the fluorescence enhancement upon restriction of molecular rotations; 5 and this increasingly popular feature can be further augmented by the introduction of ESIPT centers on the core of the AIE dyes. 6 ESIPT emitters have long been known as attractive solid-state emitters, with adaptive optical profiles depending on the environment, e.g. amorphous powders, crystals, and polymeric thin films or embedded in various matrices, such as nanoparticles or aggregates.…”

Luminescence of ESIPT-capable zinc(ii) complexes with a 1-hydroxy-1H-imidazole-based ligand: exploring the impact of substitution in the proton-donating moiety

“…The emission of ESIPT-capable dyes is highly sensitive to solvents, 43–50 substitution in the ESIPT-dye core, 51–71 protonation/deprotonation, 72–80 and coordination of metal ions. 81–96 Normally, the latter process is coupled with the deprotonation of ESIPT-dyes.…”

“…[32][33][34][35][36][37][38][39][40][41] This plethora of emissive excited states makes ESIPT-capable compounds an appealing platform for the design of multicolor luminescent materials. 42 The emission of ESIPT-capable dyes is highly sensitive to solvents, [43][44][45][46][47][48][49][50] substitution in the ESIPT-dye core, protonation/deprotonation, [72][73][74][75][76][77][78][79][80] and coordination of metal ions. [81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96] Normally, the latter process is coupled with the deprotonation of ESIPT-dyes.…”

Interplay between Dual-State and Aggregation-Induced Emission with ESIPT Scaffolds Containing Triphenylamine Substituents: Experimental and Theoretical Studies

“…It is particularly essential to gain access to synthetic intermediates, which can easily, preferentially in one step, lead to functional ESIPT derivatives with adaptative and responsive optical properties. In this context, we recently developed aryl- and heteroaryl-substituted imino-phenol (anil) compounds showing a combination of ESIPT and AIE features . These compounds can be obtained in two steps from functionalized salicylaldehydes and 1,4-phenylene diamine and, interestingly, they show a modular pH-sensitive AIE/ESIPT fluorescence color depending on the electronic nature of the substituents .…”

“…In this context, we recently developed aryl- and heteroaryl-substituted imino-phenol (anil) compounds showing a combination of ESIPT and AIE features . These compounds can be obtained in two steps from functionalized salicylaldehydes and 1,4-phenylene diamine and, interestingly, they show a modular pH-sensitive AIE/ESIPT fluorescence color depending on the electronic nature of the substituents . To build on these pioneer results, we decided to investigate salicylaldehyde derivatives, substituted at the 3- and 5-positions by triphenylamine (TPA) moieties.…”