Steering Self‐Assembly of Three‐Dimensional Iptycenes on Au(111) by Tuning Molecule‐Surface Interactions

Abstract

Self-assembly of three-dimensional molecules is scarcely studied on surfaces. Their modes of adsorption can exhibit far greater variability compared to (nearly) planar molecules that adsorb mostly flat on surfaces. This additional degree of freedom can have decisive consequences for the expression of intermolecular binding motifs, hence the formation of supramolecular structures. The determining moleculesurface interactions can be widely tuned, thereby providing a new powerful lever for crystal engineering in two dimensions. Here, we study the self-assembly of triptycene derivatives with anthracene blades on Au-( 111) by Scanning Tunneling Microscopy, Near Edge Xray Absorption Fine Structure and Density Functional Theory. The impact of molecule-surface interactions was experimentally tested by comparing pristine with iodinepassivated Au(111) surfaces. Thereby, we observed a fundamental change of the adsorption mode that triggered self-assembly of an entirely different structure.

Versatile Role of Molecule–Surface Interactions for Monolayer Self-Assembly at Liquid–Solid Interfaces: Substrate-Induced Polymorphism, Thermodynamic Stability, and New Polymorphs

“…On the other hand, the I–Au(111) surface and consequently its potential energy landscape are highly corrugated. This became evident in our previous study of an anthracene–triptycene derivate, where we inferred a strong site dependence of the adsorption energy . So in principle registry effects have the potential to selectively enhance Δ H molecule‑surface for specific lattice-matched polymorphs on the generally more weakly interacting I–Au(111) surface.…”

“…This became evident in our previous study of an anthracene−triptycene derivate, where we inferred a strong site dependence of the adsorption energy. 42 So in principle registry effects have the potential to selectively enhance ΔH molecule-surface for specific lattice-matched polymorphs on the generally more weakly interacting I− Au(111) surface. Yet, for the here studied tricarboxylic acids, we did not encounter such an intriguing exception to the rule that polymorphs with lower packing density but energetically superior H-bonding emerge on more weakly interacting surfaces.…”

“…This surface was previously introduced for studies of supramolecular self-assembly at electrified surfaces from aqueous solutions. , Adsorbates on the chemisorbed iodine monolayers become effectively decoupled from strongly interacting metal surfaces − through markedly increased adsorption heights in the absence of electronic interferences . Moreover, we have demonstrated that iodine passivation is viable to alter the adsorption geometry of three-dimensional anthracene–triptycene molecules as the starting point to steer their supramolecular self-assembly . Here, we use commercially available high quality Au(111) thin films on mica instead of single crystals.…”

“…41 Moreover, we have demonstrated that iodine passivation is viable to alter the adsorption geometry of threedimensional anthracene−triptycene molecules as the starting point to steer their supramolecular self-assembly. 42 Here, we use commercially available high quality Au(111) thin films on mica instead of single crystals. The facile preparation consists of flame annealing and subsequent dipping into aqueous potassium iodide solution, which readily results in complete coverage with a closed iodine monolayer (Supporting Information).…”

Iodine-Induced Self-Assembly Structure Transition of Organic Molecules on the Ag(111) Surface

“…The ratio between iodine and molecules can also affect the structural transformations . In addition, the adsorption of iodine as an underlying layer can change the adsorption mode of three-dimensional molecules on the Au(111) surface, resulting in a different self-assembly structure as compared with the case without the iodine layer . Furthermore, iodine can be used as a decoupling layer on the metal surface to weaken the coupling of the substrate with the molecular electronic properties. − Recently, as reported in ref , by introducing halogen atoms externally, the stoichiometric ratio of the halogen precursor can be adjusted to effectively control the surface reaction.…”