Heptagon-Containing Saddle-Shaped Nanographenes: Self-Association and Complexation Studies with Polycyclic Aromatic Hydrocarbons and Fullerenes

Abstract

Supramolecular interactions between molecules of the same or different nature determine to a great extent the degree of their applicability in many fields of science. To this regard, planar polycyclic aromatic hydrocarbons (PAHs) and their nanometric congeners, nanographenes (NGs), as well as positively curved ones, as for instance corannulene, have been extensively explored. However, negatively curved saddle-shaped NGs have remained a curiosity to date within this field. Therefore, here we communicate the first systematic study on the supramolecular behavior of heptagon-containing hexa-peri-hexabenzocoronene analogues. Thus, their self-association and host–guest complexation processes with both flat and curved PAHs, and fullerenes have been studied by means of 1H and 13C NMR titrations in solution, identifying C70 as one of the guests with the highest association constant among all the ones tested.

Ruthenium nanoparticles canopied by heptagon-containing saddle-shaped nanographenes as efficient aromatic hydrogenation catalysts

“…Thus, these remaining molecules may be organized in a second sphere of coordination, probably by π-π stacking between the aromatic rings of the hept-HBCs. 13 The surface chemistry of Ru@1 and Ru@2 was investigated by solid-state 13 C MAS-NMR with and without 1 H-13 C crosspolarization (CP). Most of the hept-HBC signals can be identified in the MAS NMR spectra of RuNPs recorded on purified samples (Figures 2a and Figure S4, see ESI section S4).…”

“…While the CO molecules located at the faces of the MNPs are normally coordinated in a bridging mode (COb), the COs placed on their edges or apexes are coordinated in a terminal mode (COt). 28 The 13 C MAS NMR spectra of solid samples of Ru@1 and Ru@2 NPs exposed to 1 bar of 13 CO Figure 1. TEM images and size histograms of (a) of Ru@1 and (c) Ru@2.…”

“…Both HRTEM images reveal the presence of crystalline RuNPs retaining the hcp structure. 13 C CP-MAS NMR spectra of Ru@1 (blue) and Ru@2 (red). (b) 13 C MAS NMR spectra of Ru@1 (blue) and Ru@2 (red) after exposure to 13 CO (1 bar, 20 h, r.t.).…”

“…11 It has also been shown that the inclusion of seven-membered rings in nanographenes leads to a saddle-shaped curvature and induces changes in optoelectronic responses and increases solubility. 12 Particular supramolecular interactions of those saddle-shaped nanographenes have been scarcely reported, 13 which might have an impact in the interaction with MNPs and the subsequent catalytic activity. Besides, to the best or our knowledge, their use as ligands for MNPs has no precedents.…”

Supramolecular Substructure of C60-Embedded Schwarzite

“…Covalently bound networks of sp 2 -hybridized carbon atoms build a plethora of topological π-structures ranging from zero-dimensional spherical fullerenes , to one-dimensional cylindrical carbon nanotubes (CNTs) and two-dimensional flat graphene, as well as three-dimensional cage-like π-networks (e.g., hypothetical schwarzite or Mackay crystals, Figure ). − Their substructures, often denoted as polycyclic aromatic hydrocarbons (PAHs) or nanocarbons, have received tremendous attention because of their aesthetic architecture and exceptional optoelectronic properties. − Such π-electron-rich nanocarbons exhibit diverse geometric configurations with different Gaussian curvatures (positive, zero, or negative). , These features endow them with the capacity for building the dispersion-driven supramolecular complexes or cocrystals with other PAHs of proper shape complementarity. − Although many examples of fullerene–PAH complexes have been isolated to date, − these structures have barely been correlated to the new type of carbon allotropes. Such supramolecular complexes could be the building blocks to gain insight into yet-unknown carbon allotropes. ,, Here we show a conceptual fullerene–schwarzite complex and isolation of its supramolecular substructure.…”