Polymorphism of Two-Dimensional Halogen Bonded Supramolecular Networks on a Graphene/Iridium(111) Surface

Abstract

The properties of 2D supramolecular self-assemblies on surfaces depend on the fine balance between molecule-substrate and molecule-molecule interactions. In this article, we study the growth of 1,3,5-tri(4'-bromophenyl)benzene (TBB) monolayer on graphene epitaxially grown on Ir(111) by means of low temperature scanning tunneling microscopy and spectroscopy (LT-STM/STS) combined with a fully atomistic 1 description of the molecules in interaction with the Gr/Ir(111) substrate, using density functional theory (DFT). In order to figure out the impact of the underlying metallic layer upon the self-assembling behavior of the molecules and their properties, we compare our results with those theoretically obtained on pristine graphene or experimentally achieved on HOPG. We demonstrated that the use of the Ir layer allows the formation of large extended, continuous and two-dimensional supramolecular networks laying even over Ir step edges like a carpet. In addition, we highlighted the obtention of two structural polymorphs never observed on HOPG. In the light of DFT simulations, we assumed that the formation of these polymorphs is driven by the balance between molecule-molecule interactions, due to Halogen bonds (XB), and the tailored molecule-surface interactions due to the presence of Ir layer.

Supramolecular Networks and Wires Dominated by Intermolecular BiEDOT Interactions

“…Moreover, π-conjugated molecules can self-assemble on surfaces in various supramolecular networks which can be observed by scanning tunneling microscopy (STM). − Multiscale transitions between different phases and surface organizations have already been evidenced with several systems. − STM studies of conformational changes at the single-molecule level have shown cis – trans isomerization of a series of molecules such as azobenzene or stilbene derivatives. Isomerization can be induced by several inputs. − Methylthiolate self-assembly and isomerization on a Au(111) surface and the direct observation of photoinduced tautomerization in single porphycene molecules on a Cu(111) surface were also recently reported. , Linear molecules can form densely close-packed or flower-like structures with cavities depending on the intermolecular interactions. ,,, Triangle-shaped molecules with different substituents form open honeycomb or flower-like structures − or close-packed stripe-like structures. ,,− We also demonstrated various organizations and on-surface isomerization of a ditopic ligand consisting of two coordinating 4-phenyl-2,2′-bipyridine entities linked through a central 9,9-dihexylfluorene bridge. The observed phase transitions were generated by protonation, and involved an intramolecular cis -to- trans -like isomerization, a change from weak to strong hydrogen bonding, and a structural phase transformation of gear chains into a stripe-like organization …”

Cross-impact of surface and interaction anisotropy in the self-assembly of organic adsorption monolayers: a Monte Carlo and transfer-matrix study

“…It is a critical limitation for our aim, since unit cells of the ordered phase in the adsorption layer usually contain a large number of molecules of large size (more than 10 atoms). However, the quantum chemistry calculations can be effectively used for the parameterization of statistical models, namely, for calculating the adsorption energies and pair interaction energies for specific molecules and surfaces, [66][67][68][69][70] e.g. e, w and D parameters for the model under consideration.…”

On-Surface Dimerization and Coordination of 4-(Bis-ethylenedioxythiophene)benzoic Acid

“…The added intermolecular/ molecular−surface interaction, the triggering conditions, and the specific environment under a microscope make on-surface reactions a different field with surprisingly novel complexes. 8,9 Scanning tunneling microscopy (STM) is employed extensively to visualize 10−17 various molecular precursors and to track the frameworks generated by on-surface reactions. 18 The reactions can therefore be investigated at a submolecular level under specific conditions in ultrahigh vacuum (UHV) or at a solid/liquid interface.…”

“…The reaction is often linked to, but different from, well-known chemical reactions in solution. The added intermolecular/molecular–surface interaction, the triggering conditions, and the specific environment under a microscope make on-surface reactions a different field with surprisingly novel complexes. , …”