Aggregation of C₇₀-Fragment Buckybowls on Surfaces: π–H and π–π Bonding in Bowl Up-Side-Down Ensembles

Abstract

The self-assembly of the C38H14-buckybowl, a fragment bowl of the C70 fullerene, has been studied with scanning tunneling microscopy on the Cu(111) surface. Isolated molecules adsorb bowl opening-up with the center C6 ring parallel to the surface. In extended 2D islands, however, 1/3 of the molecules are oriented such that the bowl opening points down. From a detailed analysis of relative orientation of the molecules, the nature of intermolecular lateral interactions is identified. In densely packed islands, π-π bonding between convex sides of the bowls dominate, while π-H bonding between rim and convex sides plays the important role in small molecular 2D clusters.

On-Surface Hydrogenation of Buckybowls: From Curved Aromatic Molecules to Planar Non-Kekulé Aromatic Hydrocarbons

“…These two configurations are observed for isolated molecules. As previously observed for the C 38 H 14 bowl, 37 tilted configurations can occur due to intermolecular interactions when two or more molecules aggregate.…”

Fivefold Symmetry and 2D Crystallization: Self‐Assembly of the Buckybowl Pentaindenocorannulene on a Cu(100) Surface

“…However, it has been shown for small aggregates (dimers, trimers, etc.) of fragment buckybowls of C 70 that intermolecular C−H⋅⋅⋅π and π⋅⋅⋅π bonding indeed come into effect on Cu(111) . As this packing motif is observed already at 50 % of the complete monolayer, the conclusion on the binding mechanism based on relative alignment seems valid.…”

As-Indaceno[3,2,1,8,7,6-Ghijklm]terrylene: A Near-Infrared Absorbing C70-Fragment

“…These signals are upfieldshifted by ca. 1 ppm compared to those of other C70 fragments, except for antiaromatic dicyclopentaperylene 2 [26][27][28][29][30][31][32][33][34][35][36] . The upfield-shifted 1 H NMR signals are characteristic for πconjugated systems with narrow HOMO-LUMO gaps 47,48 .…”

“…Consequently, C70 fragments are inherently diverse, albeit that the hitherto reported C70 fragments remain limited [26][27][28][29][30][31][32][33][34][35][36] . Among these, especially dicyclopenta[4,3,2,1-ghi:4',3',2',1'pqr]perylene (2), synthesized by Wu and co-workers, is worth mentioning 36 , as 2 exhibits distinct antiaromaticity and a narrow HOMO-LUMO gap (Figure 1b).…”