Metals Take a Walk

Do metal complexes casually stroll around certain molecules prior to chemical reactions? Scientists in the Organic Chemistry Department of the Weizmann Institute of Science have caught a glimpse of platinum-based complexes "walking" a path to their destinations.

Many types of chemical reactions and new materials depend on the integration of metals with organic (carbon based) molecules. Metals, for instance, assist in transformations of chemical compounds, while materials with many kinds of unique properties often incorporate metals into the molecular structure.

The phenomenon dubbed "ring walking," for the idea that these metal complexes might move from point to point around organic molecules (which contain the familiar, six-sided carbon rings), had been deduced from experimentation. But proving that ring walking takes place prior to a chemical transformation had not been successfully attempted before. Dr. Milko van der Boom thought that understanding the route the metal takes as it moves from one place to another on the molecule might give chemists a powerful tool for understanding and controlling chemical reactions.
 
Olena Zenkina, a student who came from Ukraine for a summer research program and ended up staying to pursue a Ph.D. in Dr. van der Boom's group, used Nuclear Magnetic Resonance (NMR) to track the movements of the platinum complexes. They were able to determine how these complexes moved in several steps around the structure of fairly simple organic molecules by undergoing weak molecular interactions at certain junctures. The walking stopped upon arrival at the point on the organic molecule where the chemical reaction occurs.
 
The results of their experiment were confirmed in a computer simulation carried out by the group of Prof. Gershom (Jan) Martin, also of the Organic Chemistry Department. Van der Boom and Zenkina are now conducting research into various aspects of ring-walking. They want to know, for instance, how fast, and how far metals can walk. In addition, they have taken the first steps toward controlling the direction a metal takes in its walk around the molecule. In contrast to today's approach to chemical transformations, which often involves custom designing sophisticated molecules, learning to direct the routes of metal complexes on the way to chemical reactions might provide a simple and effective alternative.