Size Selective Macrocyclic Catalysts

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With this award, the Chemical Catalysis and Chemical Synthesis Programs of the NSF Division of Chemistry are supporting the research of Professor Steven T. Diver of the State University of New York at Buffalo. Professor Diver is studying the development of new catalysts, the ways they react, and the use of new methods for the synthesis of biologically-active compounds such as products derived from nature (natural products). This project takes a new approach to catalysis inspired by enzymes. In organic synthesis, catalysts are used to speed up reactions and make new chemical transformations possible. In Nature, enzymes are protein-based catalysts that orient their reactive groups in three-dimensional space to facilitate a chemical reaction. Enzymes have great specificity in the starting materials they bind with as they create a microenvironment that recognizes and facilitates chemical reactions. In this project, Dr. Diver is positioning a well-known metal binding group inside a large, synthetic, molecular cavity. The cavity creates a unique chemical and spatial environment for reactions catalyzed by the bound metal. The environment surrounding the reactive metal center is being used to differentiate molecules based on their size. This approach is providing a way to gain selectivity over previously unselective chemical reactions. This project is educating scientists in a diverse and intellectually-stimulating research environment. Professor Diver is implementing a new teacher certification program designed to give new Ph.D. graduates experience in teaching that will improve outcomes at small colleges and community colleges, where quality teachers are needed. Additional outreach efforts at the elementary level include developing scientific awareness of molecules and their functions and uses in society.A major challenge in organic synthesis is the ability to differentiate reactivity between two of the same functional group. This award is addressing this problem in the context of cross alkene metathesis and other reactions through the development of new catalysts located inside macrocyclic cavities. The orientation and metal binding is provided by an N-heterocyclic carbene ligand (NHC), which is incorporated into the macrocycle. NHC ligands are highly versatile and found in many different transition metal complexes, including ruthenium (Ru) catalysts for alkene metathesis. Though a widely used and important reaction, there are limitations in cross metathesis between two alkenes that have similar reactivity. This project is utilizing size control, possible with enzymes, to differentiate alkenes - a new approach to the problem of selective cross alkene metathesis. The principle of size-selectivity is also being applied to other metal-catalyzed reactions such as palladium-catalyzed cross couplings, where size control can prevent side reactions. Cross coupling and alkene metathesis are two of the most important reactions for synthesizing new molecules such as medicinal compounds, molecular probes, natural products, and materials. Ultimately, improvements in catalysis make advanced chemical manufacturing cheaper, more predictable, and more efficient. In addition to these scientific broader impacts, this project facilitates the recruitment of students of diverse backgrounds, encourages science literacy in elementary schoolers, and enables a chemistry-specific teacher training program designed to improve preparedness and placement of new Ph.D graduates into college teaching careers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.