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

Abstract

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 photoluminescence (PL) properties of synthesized dyes were evaluated. 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 metacarborane). 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 2 the BODIPY. All these features make these dyes promising candidates for further investigations in live-cell imaging and bio-supramolecular assays.

Effects of Heavy Iodine Atoms and π‐Expanded Conjugation on Charge Transfer Dynamics in Carboxylic Acid BODIPY Derivatives as Triplet Photosensitizers

“…The strong absorption bands around 500 nm and 530 nm correspond to the S 0 →S 1 transition, while the absorption band in the shorter wavelength region between 325 nm and 450 nm correspond to S 0 →S 2 transitions for all studied compounds. In the presence of iodine atoms, it was oserved that the main absorption signal shifted to the red region of the spectrum at about 30 nm [23,30,31] . This remarkable red shift originated from the intramolecular charge transfer character of the S 1 state because of the strong coupling between the highest occupied molecular orbitals of BODIPY and iodine atoms.…”

“…In the presence of iodine atoms, it was oserved that the main absorption signal shifted to the red region of the spectrum at about 30 nm. [23,30,31] This remarkable red shift originated from the intramolecular charge transfer character of the S 1 state because of the strong coupling between the highest occupied molecular orbitals of BODIPY and iodine atoms.…”

Water-Stable Carborane-Based Eu3+/Tb3+ Metal–Organic Frameworks for Tunable Time-Dependent Emission Color and Their Application in Anticounterfeiting Bar-Coding

“…This unusual electronic structure is often highlighted by considering carboranes as inorganic three-dimensional “aromatic” analogues of arenes . In this regard, for the last 25 years, a remarkable influence of icosahedral carboranes on the photophysical properties of organic fluorophores − or in their transition metal compounds has been reported. ,− However, as far as we know, there are no reports on luminescence properties of carborane-based MOFs and therefore the antenna effect has not yet been reported for a carborane linker.…”

Physico‐chemical Properties and Anticancer Activity of Carborane‐BODIPY Conjugates: A Review

“…Starting from a different types styrenyl-containing carborane and a halogenated dipyrromethene fluorophore a set of new red-light emitting 2,6-distyrenyl-substituted carborane-BODIPY 74-77 (Scheme 15) and 79 (Scheme 16) dyes were successfully synthesized by means of a versatile Pd-catalyzed Heck coupling reaction. [63] The synthetic procedure was successfully applied for the insertion of two carborane clusters into the fluorophore core, and to extend the π-conjugation of the final molecule in a single synthetic step. The developed compounds exhibit a significant bathochromic shift compared to their parent 2,6-styrenyl disubstituted BODIPY dye DS-BDP (meso-phenyl-2,6-distyrylBODIPY) and the 3, 5-styrenyl disubstituted BODIPY analogue 3,5-BDP (meso-phenyl-3,5-distyrylBODIPY).…”