Nanostructuring of Self‐Assembled Porphyrin Networks at a Solid/Liquid Interface: Local Manipulation under Global Control

Abstract

Molecules of (5,10,15,20-tetraundecylporphyrinato)-copper(II) [(TUP)Cu] can self-assemble into four different polymorphs at the interface between highly oriented pyrolytic graphite and 1-octanoic acid. Scanning tunneling microscopy (STM) reveals that it is possible to combine the global control over monolayer structure, provided by the composition and concentration of the supernatant solution, with local control, from nanomanipulation by the STM tip. In the initially formed monolayer, with a polymorph composition governed by the concentration of (TUP)Cu in the supernatant solution, the exchange of molecules physisorbed at the solid/liquid interface with those in the liquid is very limited. By using a nanoshaving procedure at the tip, defects are created in the monolayer, and these serve as local manipulation sites to create domains of higher or lower molecular density, and to incorporate a second molecular species, (TUP)Co into the monolayer of (TUP)Cu.

Externally Applied Manipulation of Molecular Assemblies at Solid‐Liquid Interfaces Revealed by Scanning Tunneling Microscopy

“…These kinetically locked structures differed in molecular density, a parameter that could be controlled by the concentration of CuTUP in the supernatant solution at the moment of layer deposition. When a nanoshaving procedure was carried out on a CuTUP polymorph domain with certain density, underneath a supernatant solution with a concentration that would encode a polymorph of either a lower or a higher density, the domain that was shaved away was subsequently refilled with molecules from the liquid that would self‐assemble into predominantly the polymorph structure with that particular density . A similar nanoshaving procedure of a CuTUP layer under a supernatant containing a different TUP derivative (i.e., CoTUP ) resulted in the subsequent local insertion of those molecules in a surrounding domain of CuTUP molecules (Figure ).…”

Self-Assembly of Covalently Linked Porphyrin Dimers at the Solid–Liquid Interface

“…In previous work, we had constructed a variety of supramolecular assemblies of (metal-) porphyrins at solid–liquid interfaces and imaged their spatial organization with the help of liquid-STM [7]. By applying specific molecular design, we were able to precisely control the two-dimensional (2D) polymorphic behavior of these assemblies by varying the nature or the concentration of the solution in the STM experiments [22,23,24]. We also constructed 2D assemblies of catalytically active Mn(III) porphyrins and investigated their reactivity with oxygen and the epoxidation of alkenes at the single-molecule scale [25,26].…”

Unidirectional supramolecular self-assembly inside nanocorrals via in situ STM nanoshaving

“…in the presence of molecular building blocks, has emerged as a most powerful tool to create and characterize confined 2D assemblies. [23][24][25][26][27][28] In this approach a sacrificial blocking layer is locally shaved off by the probe, and molecules suspended in solution can adsorb and assemble on the exposed surface area. Previous in situ STM nanoshaving studies on graphite, both by our group and other groups, have shown a preferential molecular adsorption orientation inside the exposed surface area.…”