In this CAREER project funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Peng Liu of the Department of Chemistry at the University of Pittsburgh is developing new strategies to use computational tools to investigate mechanisms and effects of ancillary ligands in transition-metal-catalyzed reactions of unactivated starting materials, such as materials with carbon-carbon and carbon-hydrogen bonds and unactivated olefins. The goal of this research is to reveal the fundamental reactivity rules of common organometallic intermediates in these transformations and to develop new models to interpret ligand effects on reactivity and selectivity. This project's educational and outreach plan aims to maximize the power of computations to enhance learning of organic chemistry concepts and to facilitate synthetic organic chemistry research. Professor Liu's team develops virtual reality (VR) software and educational materials to visualize three-dimensional molecular structures and reaction mechanism videos in an interactive and immersive environment. The VR software and its educational modules are released to undergraduate organic chemistry students and the general public free of charge through Android and Apple app stores. This new technology may transform the way organic molecules and reactions are presented to non-experts and create a more effective approach to advance understanding of organic chemistry concepts.
This project aims to address two basic challenges in performing computational studies on transition metal catalysts: 1) the lack of mechanistic understandings in many recently developed catalytic systems, and 2) the complexities in analyzing and rationalizing computational data, in particular, the origin of ligand effects. The research investigates novel reaction pathways involving the activated organometallic intermediates formed after the C-H and C-C bond cleavage steps, and elucidates the effects of ligands, directing groups, substituents, ring strain, and norbornene and Lewis acid co-catalysts. To systematically characterize the origin of ligand effects on reactivity and selectivity, a ligand-substrate interaction model is developed. This model uses energy decomposition analysis (EDA) methods to dissect the through-space ligand-substrate interactions into chemically meaningful terms, including steric repulsion, polarization, charge transfer, and dispersion. The insights obtained from the proposed ligand-substrate interaction model are used to develop of a catalyst screening methodology for transition metal catalysts. In addition, this project establishes a platform for synthetic chemistry researchers to learn and use computational tools to support their scientific research. A spectrum of activities, including curriculum and training materials development, collaboration and student exchange, and summer research programs that target undergraduate underrepresented minority students, are incorporated in the platform. A discovery-based computational chemistry course for students with synthetic organic backgrounds is developed to provide an interdisciplinary training at the interface of organic and computational chemistry. The straightforward computational models, software tools, principles of reactivity, and the online ligand database resulting from the research activities facilitate the use of computational tools by synthetic organic chemists.
