Two-Metal Cage Comes Together

By snapping 62 building blocks together in one flask, chemists have built a nanoscale cubic cage featuring two different metals (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201202050). Their synthesis could help others build metal-organic architectures for catalysis or gas storage. Jonathan R. Nitschke and colleagues at the University of Cambridge took inspiration from biology, where chemical processes run side by side without interference. They made their cage with iron and platinum salts, along with precursors to a nitrogen-containing ligand that binds each metal in a slightly different environment. Nitschke says iron probably coordinates first, generating complexes that prevent platinum from forming anything but the desired cube. “Achieving self-assembly with different metals in a single complex is extremely difficult—very few examples are known, and they are rarely easy to handle,” says Richard J. Hooley of the University of California, Riverside, who works on similar self-assembly processes. Nitschke notes that the cage is soluble in acetonitrile, which may lead to applications complementary to those of metal-organic frameworks, which are used in the solid state. The new cage doesn’t sequester fullerenes, but Nitschke says the team has built a modified version that shows preliminary signs of binding guests.