Self-Assembly of Monosized Cyclic Nanoarchitectures under Surface Confinement

Manufacturing isolated cyclic architectures is challenging on the nanoscale because it relies on a sophisticated and precise arrangement of an extended number of molecular building blocks, which either demands an inefficient serial production or competes with energetically preferred noncyclic self-assemblies. Here, a sterically crowded molecule is employed to construct well-separated exclusively cyclic monosized nanoarchitectures on a metal surface through molecular self-assembly. Two intertwined molecules form the building block of the cyclic nanoarchitectures, a nonplanar curved dimer. The radial height gradients along the building blocks promote directional intermolecular interactions, favoring monosized cyclic widely over noncyclic self-assembly. The self-assembly mechanism is verified by low-temperature scanning tunneling microscopy imaging and manipulation, supported by large-scale ab initio calculations.