Exploring bodipy dyes in light-harvesting, energy transfer and bioinspired probe designs

Candidate: Sahana Sritharan

Supervisor: Dr. Bryan Koivisto

Abstract:

Attempts to mimic Nature and create artificial photosynthetic systems has transformed from an active chemical curiosity to a full-blown research pursuit, owing to our need for sustainable energy generation. To this end, this thesis explores the use of the dye, BODIPY (4-4’- difluoro-4-bora-3a,4a-diaza-s-indacene). BODIPY dyes have gained considerable attention owing to their highly desirable properties, such as strong absorption, fluorescence quantum yields, good chemical and photo-stability. These desirable physiochemical properties have led to materials that can be used for chemosensors, biological labeling agents, fluorescent switches, laser dyes, and organic sensitizers. For this thesis, a pentamethylBODIPY (2.1a) derivative was further functionalized in order to examine its potential for a myriad of applications.

Energy extraction in terms of dye-sensitized solar cells (DSSCs) requires electronically asymmetric molecules as building blocks. In Chapter 2, pentamethylBODIPY (2.1a) was modified using Schiff-base chemistry to create a family of dye building blocks. In this chapter, mono ß substitution was used to break symmetry in this potential BODIPY building block, thus tuning the electronic and optical properties.

Biological labelling and fluorescent probe design could benefit if the tagged fluorophore had different optical properties than the non-tagged dye, so in Chapter 3 the click reaction - conjugated directly to the BODIPY core - is explored. In this chapter, unique behavior was observed depending on the reaction conditions and location of functionalization on the pentamethylBODIPY (2.1a) core.

Inspired by photosystem II, Chapter 4 examines the potential for using a phenylacetylene macrocycle as the antennae for BODIPY. Like the protein scaffold in photosystem II that is able to hold dyes at fixed distances for effective energy transfer, this work attempts to use the tenants of supramolecular chemistry to synthesize a [2]rotaxane mimic. While synthetically not successful, this large body of work provides further insight into the limitations of using BODIPY dyes in click reactions.