Exploring the Impact of Icosahedral Carborane 3-D Aromaticity on the Photophysical Properties of Traditional Dye Structures

• Isabella Williams, Chemistry, University of Delaware

• Marco Messina, Chemistry and Biochemistry, University of Delaware

Icosahedral carboranes (C2B10H12) are a class of boron-rich cluster compounds that exist as three distinct isomers (ortho-, meta-, and para-). Carboranes are well known for their remarkable chemical and thermal stability, as well as their unique electronic properties. Carboranes have been increasingly utilized as ligands on organometallic complexes, as bioisoteric replacements of adamantane or benzene in theraputic compounds, and as components in metal-organic frameworks. Interestingly, carboranes possess “3-dimensional aromaticity”, in which the bonding electrons are fully delocalized throughout the cluster structure. Against this backdrop, our group initiated a research program investigating perturbations to photophysical parameters that arise from directly appending 3-D σ-aromatic carboranes to common dye structures, such as fluorescein and carbarhodamine. Herein, we present the synthesis of carborane-containing fluorescein and carbarhodamine dyes termed carboranylfluoresceins and carboranylcarborhodamines, respectively. We also include progress towards the creation of a carborane-based silicon-rhodamine derivative. Additionally, we compare the photophysical properties of these new carborane containing dyes to analogous fluorescein and carborhodamine fluorophores.