By Daniel Dunaief
If you build it, he will come.
That’s an iconic line from the movie “Field of Dreams,” starring Kevin Costner, in which a mythical voice calls to the Iowa farmer, encouraging him to plow through his corn to build a baseball field so the ghosts of past baseball players can entertain a modern audience.
It seems only fitting that this year, in which Major League Baseball hosted its first professional game in Iowa near the set of the popular movie, chemists have built something they hope brings together numerous other chemicals to produce products with various applications, from drug discovery to materials science.
About 120 years ago, researchers in France discovered a highly reactive gas called thionyl tetrafluoride, whose chemical symbol is SOF4.
The gas has numerous potential applications because researchers can control its reactions and derivatives. Scientists can swap each sulfur-fluorine bond with a bond between sulfur and something with desirable properties or applications.
While the gas serves as a potential building block, it is scarce and is not commercially available.
Thionyl tetrafluoride is “very reactive,” said chemist and Cold Spring Harbor Laboratory Professor John Moses. “It’s not something the Average Joe wants. It’s dangerous chemistry.” It was largely overlooked until the 1960’s, when chemists at DuPont reinvestigated it.
Once Suhua Li, the lead author of a recent paper in Nature Chemistry and a former post doctoral researcher in Nobel-prize winner K. Barry Sharpless’s lab at Scripps Research Institute in La Jolla, California, generated more of this gas, the team could work together to determine the types of connections that might be possible.
While the research was a group effort in terms of planning and ideas, Li, who did the vast majority of the synthesis of the gas, is “the hero,” Moses said. “The gas itself, and reagents used to make the gas, are potentially very dangerous, and it takes courage and confidence to attempt such chemistry. ([Li] even had a bit of a mishap, to say the least, but still went ahead and tried again.”
Moses also appreciates how “ideas are just ideas until somebody takes the initiative to put them into practice.”
Moses, Sharpless, and Scripps Research Institute Associate Professor Peng Wu developed the polymer chemistry, while Hans Zuilhof of Wageningen University in the Netherlands helped elucidate the helical structure of the polymers.
The team used a technique Sharpless calls “click chemistry” to explore the substances they could create with this gas.
Thionyl tetrafluoride acts like a lego building block that can be connected with other building blocks in several dimensions.
Click reactions create defined products with absolute reliability, Moses explained. Scientists get what they expect, which is not always true in chemistry.
“In some reactions, you take A and B and you don’t always get C,” Moses said. “You get C as a major product, but you also get D, E and F.”
In click chemistry, however, the combination of A and B is guaranteed to produce C.
Some click reactions run better in water, or at least when water is present. Water is non-toxic, inflammable, inexpensive and a good heat sink.
Click philosophy is about using reliable reactions for the purpose of function discovery.
With thionyl tetrafluoride, Li and the other researchers made about 30 polymers, each of which had original structures using different fragments.
The group managed to attach antibiotics to a thionyl tetrafluoride-derived polymer and demonstrated that it retains antibacterial function.
As long as the module has a handle to exchange with the sulfur-fluorine bond, the gas has a broad range of potential applications.
With thionyl tetrafluoride as his inspiration, Moses coined the term multidimensional click chemistry, which identifies the gas a multi dimensional hub.
The chemists used a regular party balloon to transfer the gas, which is connected to a syringe and a needle. They inserted the needle through a rubber septum into a sealed flask. The reaction with reagents in the flask is straightforward to perform once the gas is available, Moses said.
Born and raised in Wrexham, North Wales, a town aglow after actors Ryan Reynolds and Rob McElhenney last year bought a 156-year-old local soccer team, Moses had no interest in science when he was young, although he was curious about life in general.
He left school to work in a factory that made life rafts and buoyancy jackets when he was 16.
The factory had a distinct odor of toluene and glue.
“It was dreadful,” he recalls. “I was lucky to escape that life.”
He eventually landed an apprenticeship at a company called App-Chem, that allowed him to study physics and chemistry in college one day per week.