Everything from the manufacture of new materials to
the creation of modern medications relies on chemicals
known as metal-based catalysts. Catalysts pack a double
punch: Even as they greatly increase the rate of chemical
processes, they regenerate so they can be used again.
Catalysts also can be designed to break or make powerful
chemical bonds at one end of a molecule while leaving the
other end to sit quietly inactive. For this reason, many
chemists — particularly inorganic chemists who often
study metals and their reactivity — are on a
continuing quest for new catalysts.
At Johns Hopkins, researchers have developed a new set
of molecules that has the potential to catalyze a wide
variety of chemical reactions, including, but not limited
to, the cleanup of common but quite dangerous groundwater
pollutants called organohalides. Scientists announced their
results at the American Chemical Society's annual summer
meeting, held recently in Philadelphia.
"Organohalides comprise a high percentage of the
priority pollutants as registered by the EPA, so this is a
pretty important advance," said David P. Goldberg,
associate professor in the Department of
Chemistry in the Krieger School of Arts and Sciences.
"In addition, our molecules have the potential to catalyze
a number of other reactions important in the synthesis of
specialty chemicals for industry."
In the biological world, enzymes are the catalysts
that function inside cells, and many enzymes depend on
metal held inside specially built organic molecules called
porphyrins. Using these as a model, Goldberg's team
synthesized a variation that changed the properties of the
reactive metal in the center.
Called a "corrolazine," the new ring contains one less
atom than other, better-studied porphyrins. These molecules
are fascinating from a fundamental perspective, Goldberg
said. The tiny change made in their structure imparts some
very different properties than the same system found in
nature and may allow scientists to catalyze reactions in
very different ways from their natural counterparts.
"By studying these natural mimics, we can learn a
great deal about why nature — actually, evolution
— made certain choices in the design and development
of enzymes," Goldberg said.
Though some of the molecules being investigated by
Goldberg's team are important synthetic precursors that can
ultimately be used in making specialty chemicals and
pharmaceuticals, other recent work in the group,
spearheaded by graduate students Joseph Fox and David
Capretto, has focused on how to use the new catalysts to
render the groundwater pollutants called organohalides
harmless by way of a simple chemical reaction.
"Organohalides can be transformed into safer compounds
by breaking the bonds between the halogen and carbon atoms
they contain," Goldberg said.
Goldberg's work, funded largely by the National
Science Foundation, has been recognized by the Dreyfus
Foundation, which awarded him one of nine Dreyfus
Postdoctoral Fellowships in Environmental Chemistry given
out this year nationwide. These prestigious awards are
intended to fund the salary and expenses of an outstanding
postdoctoral fellow for two years in the lab of the
"Though this work represents a step forward, there is
still an enormous amount of work to be done, including
finding what metals work best under what conditions,"