The synthesis and characterization of an enantiopure superhelicene nanographene is reported in which two saddle-shaped and one planar hexabenzocoronene (HBC) units are arranged in a helicoidal shape to form an undecabenzo[7]carbohelicene. The described compound is the first fully π-extended [7]helicene. Racemic resolution of the helical nanographene permitted analysis of the chiroptical properties and revealed dissymmetry factors in the range of 2×10 both in the absorption and in the emission measurements. Remarkably, non-linear photophysical analysis demonstrated a two-photon absorption cross-section of 870 GM at 800 nm and a perfect overlap between linear, non-linear, and chiral emissions.

This feature article focuses on the bottom-up approaches (solution-phase) based on organic synthesis for the preparation of saddle-shaped distorted polycyclic aromatic hydrocarbons (PAHs). We summarise the recent progress on the synthetic strategies followed to obtain well-defined nanographenes containing heptagonal and octagonal carbocycles, highlighting the novel strategy developed by our group together with our recent contributions in the area of distorted aromatics. The presence of seven- or eight-membered rings induces a saddle-shape curvature in the planar network pushing the structure out of the plane, which influences the physical properties exhibited. Some brief details on the optical and electronic properties of these curved nanostructures are also discussed.

A new family of distorted ribbon‐shaped nanographenes was designed, synthesized, and their optical and electrochemical properties were evaluated, pointing out an unprecedented correlation between their structural characteristics and the two‐photon absorption (TPA) responses and electrochemical band gaps. Three nanographene ribbons have been prepared: a seven‐membered‐ring‐containing nanographene presenting a tropone moiety at the edge, its full‐carbon analogue, and a purely hexagonal one. We have found that the TPA cross‐sections and the electrochemical band gaps of the seven‐membered‐ring‐containing compounds are higher and lower, respectively, than those of the fully hexagonal polycyclic aromatic hydrocarbon (PAH). Interestingly, the inclusion of additional curvature has a positive effect in terms of non‐linear optical properties of those ribbons.

Au nique rippled nanographene consisting of 52 fused rings is presented in which six out-of-plane motifs are fully fused into at riangular aromatic surface with as ize of approximately 2.5 nm. Three units of an unprecedented fully lateral p-extended octabenzo[5]helicene together with three units of saddle-shaped heptagonal rings are combined in as ingle structure,l eading to aw ell-soluble warped nanographene.T he two diastereomeric pairs of possible enantiomers were isolated, and their linear,non-linear,and chiroptical properties were evaluated, revealing outstanding quantum yield and brightness values at low energy,t ogether with good chiroptical responses in both absorption and emission.

A chiral bidentate inclusion complex has been formed by halogen-bond interaction between the pyridyl moieties of a pyridoallenoacetylenic host and octafluorodiiodobutane. X-ray crystallography showed that the guest adopts a chiral conformation inside the molecular channels formed by stacking of the host units. A 10 ppm shielding of the (15)N NMR resonance for the pyridil units provided evidence of the formation of the halogen-bond complex in solution.

Chiral macrocycles offer great potential and versatility regarding their applications. They have been employed in asymmetric catalysts, as chiral sensors, and as chiral supramolecular frameworks. For these reasons, they have been attracting increasing interest over the years. Despite all of the work developed in this area, most of the reported chiral macrocycles are not conformationally stable and present weak chiroptical responses. Such features substantially limit the scope of applications for these compounds. On the other hand, we have shown that axially chiral allenes can be introduced into macrocycles, conferring conformational stability and outstanding chiroptical responses. However, these allenes photoisomerize when conjugated with electron-donating groups, hampering the possibility of synthesizing systems with tuned optical properties. To overcome all of these limitations with a single structural motif, we propose the use of spiranes to construct new stable, conformationally rigid, and chemically functionalizable macrocyclic structures with strong chiroptical responses. As a first step in this new direction, we theoretically predict the chiroptical responses for macrocycles bearing spiranes to be as strong as with their allenic counterparts. As a side product, we also test the popular Minnesota functional, M06-2X, and compare it with cam-B3LYP, which has been previously analyzed with respect to experimental data in our laboratory. Thus, we hereby propose that spiranes are a good alternative to allenes for the construction of new chiral macrocycles.

State-of-the-art chiroptical spectroscopies are valuable tools for structural elucidation. However, the potential of these spectroscopies for everyday applications has not been exploited to date partially due to the lack of sufficiently stable and efficient chiroptical systems. To this end, the development of suitable chiroptical structures is essential. Herein, we present the synthesis of spiro-compounds (P )-1 and (P )-2 as well as (M )-1 and (M )-2 exhibiting remarkable chiroptical responses. Theoretical simulations show that (P )-1, constituted by two (P)-configured spiranic chiral axes, presents an all-carbon double helix structure with (M)-helicity. On the other hand, molecular dynamic simulations reveal (P )-2 to have a single path for geometry-modification along its flat conformational space, certifying it as a chiral flexible shape-persistent macrocycle. Geometric quantification of chirality has been used to compare the spiranic derivatives presented herein.

We report the synthesis and characterization of an enantiopure superhelicene nanographene constituted by two saddleshaped and one planar hexabenzocoronene (HBC) units arranged in a helicoidal shape. This is, to the best of our knowledge, the first undecabenzo[7]carbohelicene, i.e., the first fully π-extended [7]helicene. Racemic resolution allowed its chiroptical properties analysis revealing dissymmetry factors in the range of 2×10-3 both in the absorption and in the emission measurements. Remarkably, nonlinear photophysical analysis showed two-photon absorption crosssection of 870 GM at 800 nm and a perfect overlapping between linear, non-linear and chiral emission.