Spontaneous Formation of Triptycene Supramolecules on Surfaces

Abstract

In the limit of weak molecular interaction with an inorganic surface, noncovalent interactions between molecules dominate the nucleation and thin-film growth. Here, we report on the formation of three-dimensional triptycene clusters with a particularly stable structure. Once formed at the early stage of molecular adsorption, the clusters are stable for all temperatures until desorption. Furthermore, the clusters diffuse and nucleate as individual entities, therefore constituting building blocks for the later thin-film formation. High resolution scanning tunneling microscopy images indicate that the cluster is stabilized by C-H-pi interactions. The formation of such molecular structures at a surface is possible because the three-dimensional structure of the triptycene molecule leads to a very weak and mobile adsorption state. These results show that it is possible to investigate complex pathways in the formation of three-dimensional supramolecules at surfaces using a scanning tunneling microscope.

Triptycene-terminated thiolate and selenolate monolayers on Au(111)

“…The latter has been described in the literature as an example for the limit of weak interaction with an inorganic surface [52]. This supports the assumption that intermolecular packing is the main driving force for the strong tilt of the triptycene-based molecules in the monolayers.…”

Active Intramolecular Conformational Dynamics Controlling the Assembly of Azobenzene Derivatives at Surfaces

“…However, noncovalent interactions add up when multiple connection points exist between a molecule, which may overcome the adsorption energy and favor three-dimensional (3D) structures. [8] Thus, we believe that only through the effective mediation of multiple hydrogen bonds (in addition to thermal energy) can the 3D conformational dynamics of CMA at the surface overcome the rigidity imposed by the metal surface.…”

“…A gold substrate is employed because it leads to weak molecular adsorption, thus maximizing the role of intermolecular interactions. [8] CMA is formed by an azobenzene skeleton functionalized with a carboxymethyl end group at one of the meta sites of the phenyl rings (see Figures 1 a and b). The methyl part of the end group can be easily identified in the STM images, while the carboxyl moieties, which are strongly active in the formation of intermolecular H bonds, are in charge of the recognition, selection, and locking of specific molecular shapes in ordered domains.…”

Self-Assembly Growth of an Upright Molecular Precursor with a Rigid Framework

“…However, the lateral size of the adamantane frame restricts the addition of functional groups to further control lateral interactions and the intermolecular spacing distance. Recently, Fukushima et al has reported the synthesis of trithiol tripods with a triptycene frame that self-assembles on Au(111) in the solution phase. , Triptycenes are rigid three-dimensional aromatic molecules, which provides the possibility to add multiple functionalities onto a single precursor. − However, the large size and aromaticity of triptycenes further complicates the interplay between molecule–substrate and intermolecular interactions as compared with adamantanes . Thus, in order to realize the aforementioned advantages over adamantanes, the underlying interactions in the structure of self-assembled structure of the primitive triptycene-based tripods should first be elucidated.…”