Highly ordered 2D hydrogen-bonded structures of a tetralactam macrocycle on the Au(111) surface

Monolayers of a tetralactam macrocycle, which are commonly used as building blocks in the synthesis of rotaxanes or catenanes, are deposited on a Au(111) surface by using vapor deposition. Due to self-organization, 2D highly ordered supramolecular networks form. From scanning tunneling microscopy (STM) and concomitant density-function theory calculations, two structurally different phases are found. In both phases, pairs of hydrogen bonds between the amide groups of next-neighbor macrocycles are responsible for the structural arrangement of the macrocycles. The structure of both phases differs from that of bulk lattice planes, which reveals that the Au(111) surface acts as a template for the growth of the specific 2D structures. These networks of tetralactam macrocycles possibly open a route to study mechanical interlocking processes or guest/host interactions of the molecules in further detail by using STM.