Quasicrystals are a class of ordered materials that may have symmetrical structures but lack periodicity, which means their structures don’t repeat at set intervals. Known quasicrystalline materials include metal alloys, polymers, liquid crystals, and inorganic nanoparticles. Self-assembled monolayers of organometallic compounds can also lead to quasicrystalline structures, reports a group led by S. Alex Kandel of the University of Notre Dame (Nature 2014, DOI: 10.1038/nature12993). Kandel and colleagues studied ferrocenecarboxylic acid, a sandwich compound in which an Fe2+ ion floats between two cyclopentadiene rings, one of which has a carboxylic acid group attached. The molecules assemble into pentamers held together in the center by hydrogen bonds among the carboxylic acid groups, with the cyclopentadiene rings aligned with the pentamer’s plane. Lining the sides of the pentamers are five additional pairs of molecules, also connected through their carboxylic acid groups but with their rings perpendicular to the pentamer. The pentamers could serve as building blocks for supramolecular assemblies used in materials applications in which the structures are controlled by additional functionalization of the cyclopentadiene rings, the researchers suggest.