Development of new fluorophore-tethered ortho-carborane systems: An approach for unique photophysics and applications

Abstract

The work presented in this manuscript follows with research lines initiated in the Catalysis and Inorganic Synthesis Group (LMI) at Institute of Material Sciences of Barcelona (ICMAB-CSIC), based on the synthesis, characterization and study of new boron cluster derivatives with photoluminescent properties and their potential applications. Various types of carborane functionalized fluorophores (i.e fluorene, thiophene, BODIPY, perylenediimide, truxene) have been synthesized and characterized. The photoluminescence behavior of all these systems has been studied in details and specially, the influence of the o-carborane cluster on these properties. It is important to note that in the last decade there has been a growing interest in the synthesis of molecular materials based on carborane clusters and especially in the study of their fluorescence properties, both in solution and in the solid state. The first publication related to this topic was from our group, in 2007, and since then we have been working to explore this new field within boron clusters. The contribution and progress that our group has made within this area of research has been very extensive, and in the recent years, more focused research has been carried out on the application of these materials in both optoelectronics and biomedicine. _x000D_ There are 4 chapters in results and discussion and each chapter highlights the usage of various different fluorophores such as fluorene, thiophene, perylenediimide, truxene and BODIPY dyes attached to carborane clusters with and without a spacer (alkyl chains), forming a new pi conjugated system containing donor and acceptor units. Then the starting precursors and the final compounds containing carborane units have been thoroughly studied in terms of characterization, photophysical properties which includes UV-Vis, FL, DLS, thin films, DFT, cyclic voltammetry analysis in some cases. Chapter 4 and 5 are done in collaboration with Dr. Cristina Prandi (University of Turin) and Dr. Jordi Hernando (UAB). _x000D_ Monomeric, water-dispersible nanoparticles consisting of o-carborane groups and the fluorophores (derivatives of fluorene and perylene diimide) attached to them without a spacer and with a -CH2 spacer, respectively, were prepared for the first time. These nanoparticles containing our compounds can be further investigated for possible applications in the field of biomedicine and optoelectronic devices. Along with this, we have tried to highlight some of the advantages due to the incorporation of o-carborane fractions to fluorescent systems such as higher solubility, emission induced by solid state aggregation and electron acceptance capacity of the systems. For the last chapter, the DFT studies have been carried out in collaboration with Prof. Pascal Lacroix of the Université de Toulouse, France. Our approach was to consider one arm of these three-branch systems and optimize and calculate its UV spectrum, both in the ground state and in the excited state, using the CAM-B3LYP/6-31G* method and the solvent as THF. Two-photon absorption (TPA) measurements were performed in collaboration with Dr. Jean Pierre Malval of the Université de Haute-Alsace, France, which did not give satisfactory results, probably due to low quantum efficiency. Along with the DFT calculations, the cyclic voltammetry studies showed that the HOMO and LUMO bandgap energy values ​​for all compounds were in good agreement with the TPA bandgap values. Some work in this direction is ongoing. Further work in this direction is on-going.

Date of Award	26 Oct 2022
Original language	English
Supervisor	Nuñez Aguilera, Maria Rosario (Director)