Fluorescent 2-(2′-hydroxybenzofuran)benzoxazole (HBBO) borate complexes: synthesis, optical properties, and theoretical calculations
Résumé
The multi-step synthesis, structural and optical properties of original luminescent borate complexes derived from 2-(2'-hydroxybenzofuran)benzoxazole (HBBO) are reported. Functionalization at position 3 of the benzofuran ring was readily achieved through an electrophilic cyclization key step followed by a Sonogashira cross-coupling reaction. The optical properties of the resulting boron difluoride dyes highlight different photophys. behaviors depending on the nature of the substitution at position 3 of the benzofuran core (tBu-phenylacetylene or NnBu2-phenylacetylene). The NnBu2-phenylacetylene moiety favors a sizeable intramol. charge transfer as evidenced by a strong solvatochromism; a feature further confirmed by ab initio calcns.