title: On the Fine-Tuning of the Excited-State Intramolecular Proton Transfer (ESIPT) Process in 2-(2'-Hydroxybenzofuran)benzazole (HBBX) Dyes.
abstract: Herein, a full investigation of the optical properties and first-principles calculations of a large series of original 2-(2'-hydroxybenzofuran)benzazole (HBBX) dyes is described. The electronic substitution on the π-conjugated core of the fluorophores and the nature of the heteroatom (O, S, N) was varied extensively to assess the necessary parameters to trigger a partial frustration of the excited-state intramolecular proton transfer (ESIPT) process, which results in the emission of both tautomers, that is, enol and keto (E* and K*). The optical properties, studied in solution and in the solid state, revealed the appearance of either an intense single K* or a dual E*/K* emission; a feature that is highly dependent on the electronic substitution (donating or accepting), the heteroelement, and the close environment. Subtle modifications of these parameters allowed the establishment of structure-property relationships that were successfully rationalized by first-principles calculations. In particular, the E*/K* emission intensity ratio was shown to be directly related to the free energies of the two emissive tautomers in the excited state.
authors.affiliation: Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé (ICPEES), groupe Chimie Organique pour les Matériaux, la Biologie et l'Optique (COMBO), UMR CNRS 7515, Ecole Européenne de Chimie, Polymères et Matériaux (ECPM), 25 Rue Becquerel, 67087, Strasbourg Cedex 02, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Heyer
authors.affiliation: Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé (ICPEES), groupe Chimie Organique pour les Matériaux, la Biologie et l'Optique (COMBO), UMR CNRS 7515, Ecole Européenne de Chimie, Polymères et Matériaux (ECPM), 25 Rue Becquerel, 67087, Strasbourg Cedex 02, France.
authors.forename: Karima
authors.initials: K
authors.lastname: Benelhadj
authors.affiliation: CEISAM, UMR CNRS 6230, BP 92208, 2 rue de la Houssinière, 44322, Nantes, Cedex 03, France.
authors.forename: Simon
authors.initials: S
authors.lastname: Budzák
authors.affiliation: CEISAM, UMR CNRS 6230, BP 92208, 2 rue de la Houssinière, 44322, Nantes, Cedex 03, France.|Institut Universitaire de France, 1, rue Descartes, 75005, Paris, Cedex 05, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Jacquemin
authors.affiliation: Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé (ICPEES), groupe Chimie Organique pour les Matériaux, la Biologie et l'Optique (COMBO), UMR CNRS 7515, Ecole Européenne de Chimie, Polymères et Matériaux (ECPM), 25 Rue Becquerel, 67087, Strasbourg Cedex 02, France.
authors.forename: Julien
authors.identifier: http://orcid.org/0000-0002-0629-4949
authors.initials: J
authors.lastname: Massue
authors.affiliation: Institut de Chimie et Procédés pour l'Energie, l'Environnement et la Santé (ICPEES), groupe Chimie Organique pour les Matériaux, la Biologie et l'Optique (COMBO), UMR CNRS 7515, Ecole Européenne de Chimie, Polymères et Matériaux (ECPM), 25 Rue Becquerel, 67087, Strasbourg Cedex 02, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Ulrich
keywords: benzazoles; density functional calculations; fluorescence; proton transport; solid-state reactions