Oligo(ethylene glycol) (OEG) functionalized 2-(2′-Hydroxy benzofuranyl) benzoxazole (HBBO) derivatives: Synthesis, photophysical properties and biomolecules binding studies. (February 2021)

• Record Type: Journal Article
• Authors: Felouat, Abdellah; Massue, Julien; Ulrich, Gilles
• Is Part Of: Dyes and pigments. Volume 185(2021)Part A
• Publication Date: 2021-02
• Subjects: Dyes and dyeing -- Periodicals; Pigments -- Periodicals; 667.2
• DOI: 10.1016/j.dyepig.2020.108895
• Languages: English
• ISSNs: 0143-7208

Abstract

Abstract: Two molecular fluorophores based on a 2-(2′-Hydroxybenzofuranyl) benzoxazole (HBBO) scaffold and presenting an Excited-State Intramolecular Proton Transfer (ESIPT) process are reported herein. These dyes incorporate strongly electrodonating aromatic amino groups on the benzofuranyl side, enabling the appearance of a dual fluorescence emission corresponding to the radiative decay of the excited enol (E*) and keto (K*) tautomers at high and low energy respectively. It was previously demonstrated that dual E*/K* emission could originate from a beneficial decrease of phenolic acidity upon absorption of light leading to a thermodynamic stabilization of the first excited-state. The innovation within these dyes lies in the double functionalization of the aniline moiety with 2-(2-methoxyethoxy)ethyl units which allowed a better solubilization in protic solvents, as compared to their butyl analogs while keeping strong electrodonating capacity. Their intrinsic amphiphilic character leads to a good vectorization in a wide range of solvents from toluene to PBS buffer. The investigation of the photophysical properties of these dyes in solution showed a clear dual emission in apolar solvents with the E* band gradually red-shifting along with the dipole moment of the solvent. Dual emission is also observed in the solid-state when these dyes are doped as 1% wt in PMMA or PS films. Finally, the interactions of one dye with calf-thymus ( ct )-DNA and Bovine Serum Albumin (BSA) have been explored and reveal pronounced modifications of the UV–Vis profile of the dye. Additionally, a gradual hypsofluorochromic shift and narrowing of the K* band along with the appearance of the E* fluorescence band upon addition of ct -DNA or BSA is also observed, presumably evidencing an intercalation mode of binding. Highlights: Two original HBBO emitters displaying Excited-State Intramolecular Proton Transfer (ESIPT) emission are presented. Their full photophysical characterization in solution and in the solid-state is described. Their interactions with biomolecules (DNA and BSA) are discussed.