Synthesis and Characterization of Polyhalogenated Boron Dipyrromethenes and Carboranylbisthiophene Oligomers

Abstract

Chapter 1 of this dissertation shows a brief overview of fundamental concepts and classic synthetic routes of BODIPY dyes. The synthetic strategies and various application (e.g. PDT sensitizers and fluorescent indicators) of halogenated BODIPYs are also presented in this chapter. Chapters 2-4 describe the synthesis of three new polyhalogenated BODIPY platforms and their regioselective functionalization. Such new platforms provide new methodologies for producing both symmetric and asymmetric BODIPYs. Pd(0)-catalyzed cross-couplings and aromatic substitution reactions were applied to investigate the reactivity and regioselectivity of different halogen groups on the BODIPY platforms. The studies showed that the reactivity order of the halogens under both these reaction conditions is: 8-Cl &asymp 1,7-Br > 3,5-Cl > 2,6-Cl > 4,4-F. This breakthrough in BODIPY chemistry allowed the global stepwise functionalization (up to nona-functionalization) using various organometallic reagents and (or) N-, O-, and S-centered nucleophiles. During the investigation, more than fifty new BODIPYs were prepared via Pd(0)-catalyzed cross-coupling and nucleophilic substitution reactions, which are usually very difficult or impossible to prepare using traditional methods. In summary, the synthetic method developed and the new polyhalogenated BODIPY platforms provide a facile way to introduce special groups for various applications. Chapter 5 reports the synthesis of a series of 2,2’-(o-carboranyl)bisthiophene oligomers with bromo, trimethylsilylethyne, vinyl, N-methylpyrrole or thienyl group by bromination, Sonogashira and Stille cross-coupling reactions. Among those compounds, the di(thienyl-N-methylpyrrole)-o-carborane and di(bisthienyl)-o-carborane can be successfully electropolymerized on a suitable anode to produce the corresponding conducting polymers. DFT calculations are also performed, which is consistent with the electrochemical data.