Novel Electrophilic Carbene Architectures and Related Main Group Analogs

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Carbon is the building material upon which the elements of life are constructed. A basic tenet is that carbon forms four chemical bonds. In this project, funded by the Chemical Synthesis Program of the Chemistry Division, Professor Todd Hudnall of the Department of Chemistry and Biochemistry at Texas State University - San Marcos seeks to prepare substances that violate the four-bonds per carbon principle. Specifically, compounds called carbenes that contain carbon with only two bonds are prepared. Because of the unusually low number of bonds, carbenes are very reactive and have important electronic properties. The methods that are developed to prepare the carbenes are extended to the related elements, germanium and tin. These synthetic methods potentially useful, low temperature ways to access metastable alloys. In addition to training undergraduate and graduate students, this project may ultimately result in the discovery of novel materials that may benefit society in applications ranging from quantum computing to single molecular magnets to catalysts. Professor Hudnall has maintained a collaborative outreach program with the McKenna Children’s Museum called “Laboratory Workstations.” This program engages children, ages 3-10, in hands-on simple chemistry experiments in mock gloveboxes, and is also inclusive of local chemistry students from Canyon High School. Texas State University is an Hispanic Serving Institution. This project provides research experiences to students from groups underrepresented in science. The aim of this project is to prepare electrophilic carbene ligands and related main group analogs. Sets of carbenes, whose electrophilic character and attendant pi-acidity can be systematically increased by a lowering of their respective Lowest Unoccupied Molecular Orbital (LUMO) energy levels, are targeted using computations. These compounds and related germanium and tin species with exceptionally small singlet-triplet gaps are prepared. Among these are diamidosilylenes, germylenes, stannylenes, and cationic heterocyclic carbenes. One question that is investigated is why diamidocarbenes can be photolyzed to a triplet excited state where other carbenes cannot. The photochemistry of the carbenes is explored and applications as electrophilic carbene-supported main group catalysts and as precursors for the low-temperature generation of main group alloys are developed. The program serves students from underrepresented groups by their inclusion in the research project and though outreach programs to K-12 students.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.