Science http://doi.org/mq6 (2013)

Credit: © 2013 AAAS

Chemists have long relied on spectroscopic methods to identify the composition and structure of chemical species as they react, and the products they generate. Furthermore, developments in microscopy techniques have, over the past years, made real-space imaging of molecules and surfaces with atomic resolution possible. It has therefore been a long-standing objective to combine the two approaches and directly image complex molecules as they undergo a chemical reaction. Now, a collaboration led by Michael Crommie and Felix Fischer has accomplished this feat, by using atomic force microscopy to image individual aromatic molecules placed on a silver surface as they undergo several cyclization processes on heating. By using the technique in a so-called non-contact mode it is sensitive to tiny changes of electronic charge, which allows the scientists to visualize both the carbon atoms, as well as the nature of the chemical bonds joining them together. The detailed mechanistic understanding offered by this approach holds promise for the rational design of other molecular architectures on surfaces.