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Better living through palladium

This year's Nobel Prize for chemistry was awarded for decades-old breakthroughs in the use of palladium to help synthesize useful compounds — a process that took the Royal Swedish Academy of Sciences 13 pages to explain. The easy way to explain it is to say palladium is a rare metal that acts as a catalyst or "matchmaker," marrying ingredients to produce all sorts of useful things for flat-screen displays, cancer drugs, asthma medicines and more.

"Any undergraduate who's taken chemistry is starting to see this in textbooks as really important chemistry," Joseph Francisco, president of the American Chemical Society, told me today. Francisco is a chemistry professor at Purdue University and hence a colleague of one of the laureates named today, Purdue's Ei-Ichi Negishi.


Negishi, along with the University of Delaware's Richard Heck and Hokkaido University's Akira Suzuki, were honored for their work in the 1960s and '70s to develop a technique called palladium-catalyzed cross coupling in organic synthesis. That's quite a mouthful, but it simply means they found a way to use palladium atoms to build smaller molecules into larger ones, The atoms act as "marriage brokers," in the words of Inside Science News Service's Steve Miller. Here's what Francisco told Miller:

"Think of palladium as the mutual friend who brings two people together for a handshake," Francisco said. "Palladium brings the right carbon atoms from two molecules together, performs the introduction, and then moves on."

The palladium atoms themselves emerge unchanged by the process, ready to introduce more carbon atoms to each other.

"The beautiful thing about this chemistry is it's very fundamental ... it can create new carbon bonds and certain functional groups that normally would be very difficult to create, in a very easy, very facile, very efficient way," Francisco told me.

Francisco said most chemists knew it was just a matter of time before Heck, Suzuki and Negishi won a Nobel for their work. "At the time, I don't think the Nobel laureates really anticipated just how broadly that chemistry would be applied, but it was," he said.

So what kinds of products have been created through palladium-catalyzed cross coupling?

Pharmaceuticals: Painkillers ranging from synthetic morphine to naproxen (which is marketed under brand names such as Aleve or Midol Extended Relief). Asthma medicines such as montelukast (marketed as Singulair). Anti-cancer drugs such as synthetic Taxol as well as the candidate drug discodermolide (a synthetic version of a poison found in a Caribbean marine sponge) and diazonamide A (which appears to be effective in fighting colon cancer). Potential anti-viral drugs such as dragmacidin F (which affects the herpes virus and HIV). Antibiotics such as modified vancomycin (to fight MRSA infections).

Plastics: Heck developed the chemical reaction that now bears his name in order to create styrene, a major component in polystyrene plastic.

Electronics: Reactions involving palladium are used to optimize the blue light in organic light-emitting diodes, or OLEDs, which have found their way into ultra-thin flat-screen displays. The Heck reaction also comes into play for producing resins used in electronic fabrication (such as Dow Chemical's Cyclotene).

... And more: The Heck reaction is a key step in the production of the herbicide Prosulforon. The Suzuki reaction is used to manufacture a fungicide known as Boscalid. And strangely enough, researchers reported just this year that they put palladium together with graphene, the one-atom-thick form of carbon that earned two other researchers the Nobel Prize in physics this week. Palladium-graphene hybrids could be used as catalysts for the Suzuki reaction, to produce new strains of polymer circuitry and liquid crystals.

"What's exciting about this is it's a case where fundamental chemistry has led to innovations in the chemical and pharmaceutical industries that bring benefit to the general public," Francisco said. "What can be more exciting than using fundamental chemistry to improve the lives of people worldwide? That's cool stuff."


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