The promise of self-assembled monolayers (SAMs) is far-reaching. Find a molecule that binds easily to a metal surface and, by attaching chemical functional groups to the opposite end of the molecule, you can produce a surface that combines the large-scale order of the metal with the versatility of organic chemistry. Applications range from sensors to drug delivery.
In 1983 Ralph Nuzzo and David Allara discovered that sulfur-containing molecules called thiols form SAMs on gold surfaces. (For more on the history of thiol-based SAMs and other organic thin films, see the article by Joe Greene on page 43 of this issue.) Unfortunately, though, the gold–sulfur bond is relatively weak, and thiol-based SAMs degrade in days or even hours in light, air, or many common solvents. But despite three decades of research, better options have been hard to come by.
A class of molecules called N-heterocyclic carbenes (NHCs) is emerging as an...
