In a recent study published in collaboration between UChicago and UW Madison, researchers have uncovered new insights into how nitrogen centers couple together under copper catalysis. Their work challenges conventional wisdom and opens new avenues in the field of chemical reactivity.
The study, published in the Journal of American Chemical Society, began when experimental researchers at the University of Wisconsin Madison sought the collaboration of The Gagliardi Group to help evaluate and validate a proposal regarding coupling reactions.
“They had done this reaction with copper in their lab and had a mechanistic proposal for how that worked and wanted us to evaluate that proposal with theoretical techniques,” says Daniel King, a UChicago graduate student and first author of the study.
“And what we discovered, it wasn’t what they expected.”
Predicting chemical behavior from quantum mechanics
King’s meticulous evaluation involved a combination of theoretical approaches to validate and challenge assumptions. Employing quantum chemical approaches, he aimed to model and predict the chemical behavior of the reacting copper and nitrogen centers from the underlying physical laws of quantum mechanics.
“The point is to model the quantum behavior of the electrons in a molecule by basically solving for the equation, which is the Schrodinger equation. And if you do that, or approximate the solution to that equation, you can mathematically describe electrons and then the properties of the molecule.”
However, these methods are only as powerful as they explain the experimental results.
As such, King worked meticulously with experimental collaborators to confirm the accuracy of his theoretical approach. Employing standard theoretical techniques such as density functional theory and higher-level approaches such as DMRG (density matrix renormalization group) calculations, King was able to shed light on the reactivity and behavior of the copper-nitrogen centers in unexpected ways.
Challenging expectations
UW researchers anticipated that copper and nitrogen would work together as in other couplings. But what King found instead were copper-nitrogen species that reacted far more radically and independently than presumed. It is a valuable observation and the innovation of their work, as it fundamentally alters the perspective on how these compounds react in lab settings.
“It really changes the way you see the copper species and how you think they will react. You can kind of consider these specifically copper (II) nitrogens as radicals already present, rather than as standard organometallic reactants.”
Getting to this conclusion was no small task. As the study progressed, the back and forth between researchers hammered out deficiencies in the arguments with more computations and revisions.
Despite the demands of this rigorous theoretical approach, King remained steadfast about how his results were achieved, even as evidence countered strong expectations.
“This is how science goes. People have their ideas and then it takes a rigorous process to propose and have new ideas accepted by the community,” said King.
As he nears the end of his PhD at UChicago, King is content that the study is now complete, and his work published. As his findings find footing within the field, what started as an academic exercise now holds the key to practical applications. From coupling nitrogen to producing hydrazine, a vital chemical feedstock, the implications for pharmaceuticals and various industries remain numerous and promising.
—Article originally appeared on the Department of Chemistry website