“This PCET chemistry was really interesting to us. In particular, the idea that you can use catalysts to modulate an intrinsic property of a molecule allows you to access chemical space that you couldn’t otherwise,” said Robert Knowles, an assistant professor of chemistrywho led the research.
Using PCET as a way to break strong bonds is seen in many essential biological systems, including photosynthesis and respiration, he said. Though this phenomenon is known in biological and inorganic chemistry settings, it hasn’t been widely applied to making new molecules—something Knowles hopes to change.
Given the unexplored state of PCET catalysis, Knowles decided to turn to theory instead of the trial and error approach usually taken by synthetic chemists in the initial stages of reaction development. Using a simple mathematical formula, the researchers calculated, for any pair of catalysts, the pair’s combined “effective bond strength,” which is the strength of the strongest bond they could break. Because both molecules independently contribute to this value, the research team had a high degree of flexibility in designing the catalyst system.
When they tested the catalyst pairs in the lab, the researchers observed a striking correlation between the “effective bond strength” and the reaction efficiency. While effective bond strengths that were lower or higher than the target N-H bond strength gave low reaction yields, the researchers found that matching the strengths promoted the reaction in very high yield.
“To see this formula actually working was really inspiring,” said Gilbert Choi, a graduate student in the Knowles lab and lead author on the work. Once he identified a successful catalyst system, he explored the scope of the reaction and its mechanism.
For the full article: https://blogs.princeton.edu/research/2015/07/28/new-chemistry-makes-strong-bonds-weak-jacs/