Research
Our research makes use of synthetic chemistry, mechanistic chemistry, and diverse analytical methods to understand basic scientific principles underlying photochemical phenomena in organized molecular architectures. Because photosynthesis is paradigmatic our chief focus concerns the fundamental chemistry of tetrapyrrole macrocycles.
Synthetic chemistry
We have been working to develop molecular building blocks of naturally occurring tetrapyrrole macrocycles. Such macrocycles (heme, chlorophylls, bacteriochlorophylls, vitamin B12, F430) are Nature’s most important cofactors and perform unique photochemical, redox, and catalytic functions. We have developed powerful new de novo routes for the synthesis of porphyrins and chlorins; our chief focus now concerns bacteriochlorins, which are of interest for applications in the life sciences, photomedicine, and materials science. Synthetic methodology development in this heterocyclic domain requires robust routes that are simple, scalable, and have broad scope. At present, acyclic reactants are converted via a concise 8-step synthesis to bacteriochlorins wherein the pyrroline rings are locked via geminal dimethyl groups. Subsequent derivatization elaborates the bacteriochlorins for building block applications. New synthetic routes to this fascinating class of compounds are under intense development.
Artificial photosynthesis
Artificial photosynthesis embodies the longstanding “green” challenge to harvest sunlight for mankind’s uses, in other words, to create photosynthetic-like processes in purely chemical constructs. We have been using tetrapyrrole building blocks of porphyrins, chlorins, and bacteriochlorins in elaborate molecular architectures for efficient light-harvesting. We also are exploring how to create hybrid architectures that combine natural light-harvesting proteins with synthetic chromophores to address a number of fundamental questions about light-harvesting phenomena. We also continue to develop databases for incorporation into PhotochemCAD. The spectroscopic studies of the artificial photosynthetic constructs are carried out by our longtime collaborators David F. Bocian and Dewey Holten.
Origins of life
The question of the origin(s) of life remains one of the great unsolved problems of modern science. We are investigating photochemical processes of relevance to the creation of prebiotic molecules and as an energy source to drive prebiotic molecular evolution. A key challenge is to understand the molecular requirements for the origin of the essential pigments (e.g., proto-chlorophylls) of relevance for the emergence of an early (Hadean- or Achaean-era) proto-photosynthesis. Key questions to address include how specific molecules emerged and were selected from the vastness of chemical space? To what extent do such molecules self-organize in lipid assemblies to give functional, phototrophic entities? This project encompasses a broad range of skills including organic, inorganic, bioanalytical, and biophysical chemistry.