Tapping into the Full Potential of Light to Enable Chemical Synthesis

Chemical synthesis enables other sciences, and often its development is paramount to their success. This project seeks to develop new strategies for chemical synthesis. Visible light carries with it an enormous amount of energy, the equivalent to heating a reaction to nearly 35,000 oC.  However, most molecules do not absorb this light, and are unaffected by it.  Furthermore, only a few strategies for harvesting this photochemical energy exist, and they focus on energy generation or storage. Little attention has been paid to exploiting this energy for the purposes of indirect chemical synthesis.  Nature provides an elegant example of indirect chemical synthesis in photosynthesis, which utilizes light to facilitate endergonic synthesis, and ultimately, all biological synthesis.  Nature utilizes just a couple of photochemical reactions to build high energy molecules which are then consumed in dark reactions to drive thermal synthesis.  Furthermore, nature has a well-developed system that couples the “spending” and “recycling” of this energetic currency, which allows what would otherwise be engergonic reactions to take place.  With this in mind, our efforts have been capitalize on the ability of photocatalysts to absorb visible light and convert it into useable forms of energy.  Specifically, we aim to engineer small molecules that convert light energy into chemical energy that can then be used to facilitate unprecedented bond formation.  Upon reaction, the small molecules release vast amounts of energy, which results in fast and facile chemistry, and enables reactions to take place that would be otherwise energetically impossible due to either thermodynamic or kinetic reasons.  We will discuss our work involving engergonic alkene isomerization, and the formation and use of trans-cyclohexene and trans-cycloheptenes.  This work provides new conceptual strategies to synthesize small molecules of biological relevance, perform endergonic catalysis, and perform photoconjugation chemistry with spatio-temporal control.