Nazario Martín

Fullertubes, that is, fullerenes consisting of a carbon nanotube moiety capped by hemifullerene ends, are emerging carbon nanomaterials whose properties show both fullerene and carbon nanotube (CNT) traits. Albeit it may be expected that their electronic states show a certain resemblance to those of the extended nanotube, such a correlation has not yet been found or described. Here it shows a scanning tunneling microscopy (STM) and spectroscopy (STS) characterization of the adsorption, self‐assembly, and electronic structure of 2D arrays of [5,5]‐C 90 fullertube molecules on two different noble metal surfaces, Ag(111) and Au(111). The results demonstrate that the shape of the molecular orbitals of the adsorbed fullertubes corresponds closely to those expected for isolated species on the grounds of density functional theory calculations. Moreover, a comparison between the electronic density profiles in the bands of the extended [5,5]‐CNT and in the molecules reveals that some of the frontier orbitals of the fullertube molecules can be described as the result of the quantum confinement imposed by the hemifullerene caps to the delocalized band states in the extended CNT. The results thus provide a conceptual framework for the rational design of custom fullertube molecules and can potentially become a cornerstone in the understanding of these new carbon nanoforms.

The bottom‐up synthesis of 3D tetrakis(hexa‐peri‐hexabenzocoronenyl)methane, “tetrahedraphene”, is reported. This molecular nanographene constituted by four hexa‐ peri ‐hexabenzocoronene (HBC) units attached to a central sp 3 carbon atom, shows a highly symmetric arrangement of the HBC units disposed in the apex of a tetrahedron. The X‐ray crystal structure reveals a tetrahedral symmetry of the molecule and the packing in the crystal is achieved mostly by CH⋅⋅⋅π interactions since the interstitial solvent molecules prevent the π⋅⋅⋅π interactions. In solution, tetrahedraphene shows the same electrochemical and photophysical properties as the hexa‐ t Bu‐substituted HBC ( t Bu‐HBC) molecule. However, upon water addition, it undergoes a fluorescence change in solution and in the precipitated solid, showing an aggregation induced emission (AIE) process, probably derived from the restriction in the rotation and/or vibration of the HBCs. Time‐Dependent Density Functional Theory (TDDFT) calculations reveal that upon aggregation, the high energy region of the emission band decreases in intensity, whereas the intensity of the red edge emission signal increases and presents a smoother decay, compared to the non‐aggregated molecule. All in all, the excellent correlation between our simulations and the experimental findings allows explaining the colour change observed in the different solutions upon increasing the water fraction.