Red light-emitting Carborane-BODIPY dyes: Synthesis and properties of visible-light tuned fluorophores with enhanced boron content

• Published in: Dyes and pigments 2021-10, Vol.194, p.109644, Article 109644
• Main Authors: Bellomo, Chiara, Zanetti, Davide, Cardano, Francesca, Sinha, Sohini, Chaari, Mahdi, Fin, Andrea, Maranzana, Andrea, Núñez, Rosario, Blangetti, Marco, Prandi, Cristina
• Format: Article
• Language: English
• Subjects: BODIPY; Carborane; Dyads; Heck coupling; Photoluminescent material
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2021.109644

A small library of 2,6- and 3,5-distyrenyl-substituted carborane-BODIPY dyes was efficiently synthesized by means of a Pd-catalyzed Heck coupling reaction. Styrenyl-carborane derivatives were exploited as molecular tools to insert two carborane clusters into the fluorophore core and to extend the π-conjugation of the final molecule in a single synthetic step. The synthetic approach allows to increase the molecular diversity of this class of fluorescent dyes by the synthesis of symmetric or asymmetric units with enhanced boron content. The structural characterization and the photoluminescence (PL) properties of synthesized dyes were evaluated, and the structure/properties relationships have been investigated by theoretical calculations. The developed compounds exhibit a significant bathochromic shift compared to their parent fluorophore scaffolds, and absorption and emission patterns were practically unaffected by the different substituents (Me or Ph) on the Ccluster atom (Cc) of the carborane cage or the cluster isomer (ortho- or meta-carborane). Remarkably, the presence of carborane units at 2,6-positions of the fluorophore produced a significant increase of the emission fluorescent quantum yields, which could be slightly tuned by changing the Cc-substituent and the carborane isomer, as well as introducing ethylene glycol groups at the meso-position of the BODIPY. [Display omitted] •Straightforward insertion of two carborane cages and concomitant π-conjugation extension of the fluorophore in a single step.•Enlarged molecular diversity of the fluorescent dyes achieved with the synthesis of symmetric and asymmetric units.•The enhanced boron content of the dyes improves their prospective usefulness as boron carriers for BNCT applications.