Tuning the Photophysical Properties of Push‐Pull Azaheterocyclic Chromophores by Protonation: A Brief Overview of a French‐Spanish‐Czech Project

Abstract

An account is provided of our studies on the effect that the addition of acid has on the photophysical properties of π-extended push-pull chromophores that incorporate azaheterocyclic rings as electron-withdrawing moieties. The work carried out to afford white light-emitting materials based on an equilibrium between neutral and protonated forms that emit complementary colors is described. R e v i s e d m a n u s c r i p t 2 Biographical sketches Sylvain Achelle received his PhD in organic chemistry in 2007 from INSA Rouen (France). After two post-doctoral stays at the Universidad de Castilla-La Mancha (Spain) and Institut Curie (France), he was recruited as associate professor at IUT Lannion, University of Rennes 1, in 2010. He obtained the habilitation to direct research in 2014. His main research topics include the luminescence and nonlinear optical properties of organic and organometallic heterocyclic derivatives. He has published 60 scientific articles (h-index: 23 according to Web of Science) and he is currently associate editor of the journal Dyes & Pigments. Julián Rodríguez López studied chemistry at the Universidad Complutense de Madrid (UCM) and obtained his PhD with honors (cum laude) in 1990. He was a Fulbright postdoctoral fellow at the University of Texas at Austin for one year, under the supervision of Professor Philip Magnus. After successive positions at the UCM, he joined the Universidad de Castilla-La Mancha at Ciudad Real in 1995, where he is currently full professor in organic chemistry. His research concerns the synthesis and photophysical properties of novel πconjugated systems, especially dendrimers and diazine derivatives.

The effect of protonation on the excited state dynamics of pyrimidine chromophores

“…More specifically, organic chromophores with nitrogen containing heterocycles such as pyridines, [23][24][25][26][27][28] pyridazines, 23,29,30 pyrimidines 23,[31][32][33][34] and pyrazines 23,[35][36][37] are susceptible to protonation, resulting in new species with bathochromically shifted spectra. These heterocycles constitute electron accepting groups in D-π-A structures which result in efficient Intramolecular Charge Transfer (ICT) and are potential candidates for application in optoelectronics, sensors and non-linear optics.…”

Push–Pull (Iso)quinoline Chromophores: Synthesis, Photophysical Properties, and Use for White‐Light Emission

“…Conjugated push-pull chromophores based on azaheterocyclic fragments have been intensively investigated in recent years. 1,2,3,4,5 Indeed, the photophysical properties of these materials can be easily tuned by environmental stimuli such as polarity, 6,7,8,9 pH, [8][9][10]11 or the presence of metal cations. 12 Six-membered nitrogen heterocycles such as pyridine, 6,13 quinoline 3 or (benzo)diazines [1][2][3][4][5] act as moderate-to-strong electron-withdrawing groups.…”

“…15,16,17 The protonation of azaheterocyclic push-pull chromophores generally leads to a bathochromic effect on the absorption spectrum. 8,9,14 However, the effect is less predictable for the emission.…”

“…Quenching is generally observed but in some cases a red shift accompanied by either an increase or decrease in the intensity can be obtained. 8 There is currently great interest in obtaining white light emission. 18 Pure white light was defined in 1931 by the Commission Internationale de l'Eclairage (CIE) and it corresponds to CIE chromaticity coordinates of (0.33, 0.33).…”

Investigation on Photophysical, Solvatochromism and Biological Significance of Substituted 2H‐Indazole Derivatives

“…[31,[32][33][34] Moreover, these molecules known to exhibit reversible protonation behavior, resulting in induced photoluminescence in solution and solid phase, paving way for the development of colorimetric sensors. [35] Similarly, phosphorous and nitrogen containing pyrenes exhibit redox properties with tunable multi-color photoluminescence. [36] It is well known that optical spectroscopy is one of the most valuable tools for developing sensor probes for monitoring toxic metal ions, small molecules and many biological processes and events.…”