Collaborative Research: CAS: Mechanochemistry of Metallocenes

Duke University, Durham NC

Investigators

Abstract

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Chuanbing Tang of the University of South Carolina (UofSC) and Professor Stephen L. Craig of Duke University will develop a class of metal-containing polymers that respond with chemical changes under mechanical stress. Common techniques in the manufacturing of household plastics can be modified to prepare these polymers. Mechanical stress is a nearly ubiquitous feature of the environment experience by polymers. The translation of mechanical stress to responsive chemistry may provide new pathways to open up applications such as catalysis and advanced materials. This work has the potential to develop synthetic polymers that are mechanically responsive and thermally stable, both of which are important for reusability and recyclability of most commodity polymers. The impact of this work will be further broadened through its close integration with both new and existing outreach programs and educational activities at the high school, undergraduate, and graduate student level. These programs are enriched by partnerships with American Chemical Society Project SEED summer research program, ACS polymer student chapter, and local Historically Black Colleges and Universities. Joint research exchanges will be offered to participating students at UofSC and Duke to enhance their research experiences and expand future career paths. This project is focused on developing synthetic approaches toward main-chain metallocene-containing polymers and studying their mechanochemical reactivity. Metallocenes have recently emerged as a new class of mechanophores. The research aims to consolidate the evolving knowledge of mechanochemistry and expand it to new frontiers of research through the collaborative efforts using synthetic metallocene chemistry and polymer mechanochemistry. Catalytic chemistry will be explored for C-H functionalization and redox isomerization via the formation half-sandwich metal complexes. Sensitization of metallocene mechanophores will be further achieved in metallocenophane macrocycles by combining distal conformational locks and counterion assistance and quantifying their interplay on reactivity through single molecule force spectroscopy. Importantly, constructive mechanochemistry will be pursued by using reconstructive processes to make the activation of metallocenes reversible and by employing DFT calculations to elucidate thermodynamic equilibria between dissociated states and sandwich constructs. The overarching goal of this work is to understand the mechanisms and structure-activity relationships underlying the highly selective mechanochemical scission of metal-cyclopentadienyl bond. 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.