Supermolecular Wizardry

An international research team has wrapped thiolate-protected groups of gold atoms into benzene-like rings and DNA-like helices that are too small to be considered nanoparticles, but too big to be thought of as molecules (Sci. Adv. 2015, DOI: 10.1126/sciadv.1500425). These structures, which are stable in solution, could be useful for catalysis, biosensing, and drug delivery, says team leader Rongchao Jin of Carnegie Mellon University. And if that weren’t enchanting enough, the newly synthesized superstructures are also known as magic-sized clusters because they are made from an especially stable “magic number” of gold atoms—40 for the rings and 52 for the helices. Magic-sized gold clusters first bewitched researchers years ago, Jin tells C&EN, but the previously synthesized structures are best described as superatoms. In those structures, gold atoms contribute electrons to build a cluster with a stable electronic configuration, essentially filling superatomic valence shells. In the new structures, tetrahedrons of gold atoms act as the primary, electron-donating units, with gold-thiolate staples holding the polyhedrons together. Rather than superatoms, Jin says, these new structures are supermolecules.