Supramolecular Organization and Chiral Resolution of p‐Terphenyl‐m‐Dicarbonitrile on the Ag(111) Surface

Abstract

The supramolecular organization and layer formation of the non-linear, prochiral molecule [1, 1';4',1'']-terphenyl-3,3"-dicarbonitrile adsorbed on the Ag(111) surface is investigated by scanning tunneling microscopy (STM) and near-edge X-ray absorption fine-structure spectroscopy (NEXAFS). Upon two-dimensional confinement the molecules are deconvoluted in three stereoisomers, that is, two mirror-symmetric trans- and one cis-species. STM measurements reveal large and regular islands following room temperature deposition, whereby NEXAFS confirms a flat adsorption geometry with the electronic pi-system parallel to the surface plane. The ordering within the expressed supramolecular arrays reflects a substrate templating effect, steric constraints and the operation of weak lateral interactions mainly originating from the carbonitrile endgroups. High-resolution data at room temperature reveal enantiormorphic characteristics of the molecular packing schemes in different domains of the arrays, indicative of chiral resolution during the 2D molecular self-assembly process. At submonolayer coverage supramolecular islands coexist with a disordered fluid phase of highly mobile molecules. Following thermal quenching (down to 6 K) we find extended supramolecular ribbons stabilised again by attractive and directional noncovalent interactions, the formation of which reflects a chiral resolution of trans-species.

Functionalized Graphdiyne Nanowires: On‐Surface Synthesis and Assessment of Band Structure, Flexibility, and Information Storage Potential

“…Furthermore, the antiparallel alignment of the polar groups results in the relative displacement of one covalent chain against the other along the main chain direction such that the butadiyne sections of one wire (marked blue) are lining up with the terphenyl sections of the second wire (marked red). Similar binding motifs have been observed before for a related carbonitrile‐terphenyl species or in the double‐strand formation with carboxylic acid units A recent theoretical analysis quantified that each CN group contributes with a binding energy of around 0.1 eV. Accordingly, oligomeric double chain segments should exhibit a significant temperature stability due to accumulated interchain bonding.…”

Surface‐Confined Self‐Assembly of Di‐carbonitrile Polyphenyls

“…In contrast, the bent, nonlinear linkers are prochiral and thus can display a multiplicity of distinct network elements due to the symmetry‐breaking effect of the surface. Using a nonlinear linker featuring an increased conformational phase space due to the positioning of the CN moieties at meta positions ( m NC‐Ph 3 ‐ m CN) ( Figure a) the supramolecular organization and layer formation of the prochiral molecule absorbed on the Ag(111) surface was investigated 36…”

“…c) High‐resolution STM images of a densely packed highly ordered molecular island on the Ag(111) substrate composed of L ‐ trans molecules (top) and D ‐ trans molecules (bottom). Adapted with permission 36…”

Achieving chiral resolution in self-assembled supramolecular structures through kinetic pathways

“…As an as-deposited sample warmed up, molecules were dissociated from the edges of chevron islands. It has been reported that such edge dissociation can occur at about 300 K, including molecular systems that have stronger intermolecular bonds (about 1 eV per molecule) than DBAQ bonds, and that well-ordered molecular structures coexist with a disordered 2D liquid phase of molecules [33][34][35]. Likewise, DBAQ molecules may have a 2D liquid phase at 300 K that coexists with chevron structures.…”