Science frontiersTransforming acids into bases

Chemists at the University of California, Riverside have accomplished in the lab what until now was considered impossible: transform a family of compounds which are acids into bases.

We remember from our chemistry lab sessions that acids are substances that taste sour and react with metals and bases (bases are the chemical opposite of acids). For example, compounds of the element boron are acidic while nitrogen and phosphorus compounds are basic.

The research, reported in the 29 July of Science, makes possible a vast array of chemical reactions – such as those used in the pharmaceutical and biotechnology industries, manufacturing new materials, and research academic institutions.

“The result is totally counterintuitive,” said Guy Bertrand, a distinguished professor of chemistry, who led the research. “When I presented preliminary results from this research at a conference recently, the audience was incredulous, saying this was simply unachievable. But we have achieved it. We have transformed boron compounds into nitrogen-like compounds. In other words, we have made acids behave like bases.”

A University of California, Riverside release reports that Bertrand’s lab at UC Riverside specializes on catalysts. A catalyst is a substance – usually a metal to which ions or compounds are bound – that facilitates or allows a chemical reaction, but is neither consumed nor altered by the reaction itself. Crucial to the reaction’s success, a catalyst is like the car engine enabling an uphill drive. While only about thirty metals are used to form catalysts, the binding ions or molecules, called ligands, can number in the millions, allowing for numerous catalysts. Currently, the majority of these ligands are nitrogen- or phosphorus-based.

“The trouble with using phosphorus-based catalysts is that phosphorus is toxic and it can contaminate the end products,” Bertrand said. “Our work shows that it is now possible to replace phosphorus ligands in catalysts with boron ligands. And boron is not toxic. Catalysis research has advanced in small, incremental steps since the first catalytic reaction took place in 1902 in France. Our work is a quantum leap in catalysis research because a vast family of new catalysts can now be added to the mix. What kind of reactions these new boron-based catalysts are capable of facilitating is as yet unknown. What is known, though, is that they are potentially numerous.”

Bertrand explained that acids cannot be used as ligands to form a catalyst. Instead, bases must be used. While all boron compounds are acids, his lab has succeeded in making these compounds behave like bases. His lab achieved the result by modifying the number of electrons in boron, with no change to the atom’s nucleus.

“It’s almost like changing one atom into another atom,” Bertrand said.

His research group stumbled upon the idea during one of its regular brainstorming meetings.

“I encourage my students and postdoctoral researchers to think outside the box and not be inhibited or intimidated about sharing ideas with the group,” he said. “The smaller these brainstorming groups are, the freer the participants feel about bringing new and unconventional ideas to the table, I have found. About 90 percent of the time, the ideas are ultimately not useful. But then, about 10 percent of the time we have something to work with.”

The release notes that the research was supported by grants to Bertrand from the National Science Foundation and the U.S. Department of Energy.

Bertrand was joined in the research by Rei Kinjo and Bruno Donnadieu of UCR; and Mehmet Ali Celik and Gernot Frenking of Philipps-Universitat Marburg, Germany.

UCR’s Office of Technology Commercialization has filed a provisional patent application on the boron-based ligands developed in Bertrand’s lab.

— Read more in Rei Kinjo et al., “Synthesis and Characterization of a Neutral Tricoordinate Organoboron Isoelectronic with Amines,” Science 333, no. 6042 (29 July 2011): 610-13 (DOI: 10.1126/science.1207573)