Tehshik Peter Yoon | University of Wisconsin, Madison
Sunshine Superstar
Tehshik Yoon imagines two scenes to illustrate his newest work with photochemistry. One shows a traditional chemical park with vats of toxic chemicals, smokestacks and nasty pollutants. The other shows fields with sunlight shining down on them, making chemical reactions go.
"Light is cheap and abundant," he said. "It's environmentally friendly and renewable. So light is close to being a perfect reagent." A reagent is a substance introduced to make a molecule undergo a chemical reaction.
Yoon's research at the chemistry department at the University of Wisconsin-Madison Organic involves a new role for light in reactions. Traditional methods use UV light, which is potentially more harmful. He prefers to employ sunlight to perform a reaction called a cycloaddition. When you combine two molecules, each with a carbon-carbon double bond, to create a four-member ring, it's called a two-plus-two addition. Four-membered rings are a feature of antibiotic drugs like penicillin.
"We have shown that sunlight can do the same thing," he said. "Our take on it is to use a metal catalyst to help translate light energy into chemical energy."
Yoon employs a metal dye used in solar cells as a catalyst to absorb visible light and turn it into chemical energy. "It's the quintessential light-driven reaction," Yoon says. "We 're trying to show that we can do it better, faster, cheaper."
He adds: "For now, we're interested in the fundamental chemistry, but it may have big applications in the future. We're in the business of making hammers, not building houses."
Environmentally responsible synthetic chemistry has been a theme of research in his group. He has found ways to employ industrially friendly metals, like copper, to replace more toxic heavy metals, like chromium, in synthetic organic chemistry.
In one case, he has found a way to install oxygen and nitrogen atoms onto specific locations in an organic molecule. Existing ways of placing those atoms, as part of making, for example, a new drug, are unselective and require toxic and expensive heavy metal catalysts. He has found ways to correctly configure those atoms, which has been a challenge for synthetic chemists, using inexpensive and relatively nontoxic copper catalysts.
"The wrong configuration of, say, a drug candidate can cause it to bind to the wrong protein," Yoon explained. He has combined his knowledge of organic chemistry with a knack for coming up with the right catalyst. "We have a unique solution. We take oxidants that are not very good and make them more powerful oxidants."
Yoon has been exploring better catalysts for more than 10 years, since his undergraduate days at Harvard, through doctoral work at Caltech and into post-doctoral work back at Harvard.
Education Component
Yoon's enthusiasm extends from his research to a new teaching wrinkle that he may have invented: office hours anytime, by instant messaging.
In his lab on the fifth floor of the University of Wisconsin-Madison's chemistry building, if you looked carefully some evening, you'd see something rare for a researcher: a Blackberry on the counter, ready to receive instant messages -- from his students. "They aren't going to leave their jobs or travel back to campus just to find me during my office hours," he explains. "I want them to message me when they are trying to do their homework. That's when they need an answer."
