Sterically Hindered 2‐(2’‐Hydroxyphenyl)benzoxazole (HBO) Emitters: Synthesis, Spectroscopic Studies, and Theoretical Calculations

Timothée Stoerkler (1) , Thibault Pariat (1) , Adèle Laurent (2) , Denis Jacquemin (2) , Gilles Ulrich (1) , Julien Massue (1)

1 ICPEES - Institut de chimie et procédés pour l'énergie, l'environnement et la santé
2 CEISAM - Chimie Et Interdisciplinarité : Synthèse, Analyse, Modélisation

We describe various synthetic pathways to introduce sterically hindered substituents (mesityl, 2,4,6-triisopropylphenyl, anthracene) to the proton donor side of excited-state intramolecular proton transfer (ESIPT)-capable 2-(2’-hydroxyphenyl) benzoxazole (HBO) fluorophores. Two original synthetic approaches were investigated in order to synthesize seven HBO derivatives. Optimization studies concluded that electron rich and bulky phosphine ligands are required to ensure completion of the Suzuki-Miyaura cross-coupling reaction involving a bulky aromatic boronic acid. The photophysical properties of all dyes revealed a strong influence of the nature of the solvent on the optical properties, as protic solvents tend to stabilize enol tautomers and induce dual emission. Our studies confirmed that, unlike the majority of organic dyes, ESIPT fluorophores do not undergo π-stacking in the solid-state. The nature of the excited-states was explored by ab initio calculations.

Mots clés: Ab initio calculations; Fluorescence; Palladium; Catalysis; Steric hindrance

Domaines: Chimie organique; Chimie théorique et/ou physique

Timothée Stoerkler, Thibault Pariat, Adèle Laurent, Denis Jacquemin, Gilles Ulrich, et al.. Sterically Hindered 2‐(2’‐Hydroxyphenyl)benzoxazole (HBO) Emitters: Synthesis, Spectroscopic Studies, and Theoretical Calculations. European Journal of Organic Chemistry, 2022, 2022 (30), pp.e202200661. ⟨10.1002/ejoc.202200661⟩. ⟨hal-03853150v1⟩