Bioinspired Strongly Coupled BODIPY Arrays and Their Application in Energy and Electron Transfer Arrays

Abstract

Photosynthesis is Nature's way of efficiently converting solar radiation into chemical energy and is a main inspiration to develop environmentally friendly energy sources as an alternative to fossil fuels. Development of efficient, bioinspired artificial solar energy conversion systems require further understanding of the design principles and photophysics of natural photosynthesis. Natural photosynthesis utilizes a series of excitonically coupled photo- and redox-active molecules to provide efficient light harvesting and charge separation where these two processes are the initial key steps to convert solar radiation into chemical energy. The strong electronic interactions between individual light harvesting pigments and redox-active molecules appear to play a crucial role in efficiency of both energy transfer and charge separation. Therefore, understanding the role of the strong electronic interactions between pigments and redox-active molecules appears to be critical for the development of a novel generation of systems for solar energy conversion which mimics the efficiency of the natural system. Taking inspiration from Nature, we designed a series of arrays containing strongly electronically interacting BODIPY derivatives. We utilized BODIPY due to its favorable optical and photochemical properties and ease of availability. First, we developed a series of BODIPY arrays containing varying degrees and modes of electronic interactions (though-bond, through-space, and a combination of both) between BODIPY subunits. Here we tuned the extent of excitonic coupling by utilizing different linkers between BODIPY subunits. Of the arrays investigated, BODIPY linked via a maleimide linker provided the strongest excitonic coupling. Next, we incorporated the maleimide linked BODIPY dimer into multichromophoric arrays to determine if the strongly coupled BODIPY dimer could function as a light harvesting component. We developed a series of BODIPY-Chlorin arrays where the strongly coupled BODIPY dimer functions as an energy donor and transfers the excited state energy to the chlorin energy acceptor in ~ 10 ps time scale. Lastly, we developed a model strongly coupled BODIPY array in which picosecond charge separation occurs. Overall, we show that strongly coupled BODIPY arrays are promising candidates for artificial solar energy conversion systems.