Nanographenes as electron-deficient cores of donor-acceptor systems

Abstract

Conjugation of nanographenes (NGs) with electro-active molecules can establish donor-acceptor π-systems in which the former generally serve as the electron-donating moieties due to their electronic-rich nature. In contrast, here we report a series of reversed donor-acceptor structures are obtained by C–N coupling of electron-deficient perchlorinated NGs with electron-rich anilines. Selective amination at the vertexes of the NGs is unambiguously shown through X-ray crystallography. By varying the donating ability of the anilino groups, the optical and assembly properties of donor-acceptor NGs can be finely modulated. The electron-deficient concave core of the resulting conjugates can host electron-rich guest molecules by intermolecular donor-acceptor interactions and gives rise to charge-transfer supramolecular architectures.

Polycyclic aromatic hydrocarbons in the graphene era

“…Apart from the electronic effect upon chlorination, it also provides a new entry to the functionalization and derivatization of nanographene molecules. For instance, Tan et al [237] demonstrated selective amination at the vertexes of the chlorinated nanographene molecules 157 and 159 through palladium-catalyzed Buchwald-Hartwig C-N cross-couplings ( Figure 33). The resulting structures 163 and 164 were revealed by X-ray crystallography, representing a new type of donor-acceptor nanographene molecules, of which the optical and assembly properties can be finely modulated by varying the anilino groups.…”

The Buchwald–Hartwig Amination After 25 Years

“…This strategy has also been applied in the preparation of B,N‐containing polycyclic aromatic hydrocarbons such as 25 , which are of potential relevance for implementation in optoelectronic devices. Additionally, the amination of the vertexes of well‐defined nanographenes provided an entry to reversed donor‐acceptor conjugates such as 26 , whose electron‐deficient cavity can host electron‐rich guests as a result of intermolecular charge transfer. In a different example, the sixfold Buchwald–Hartwig amination of a 9,10‐diaminoanthracene derivative with 1,4‐dibromobenzene afforded hexaaza[1 6 ]paracyclophane 27 .…”

Bowl Inversion in an Exo‐type Supramolecule in the Solid State

“…We began our study by investigating the assembly in solution between 1 and 2 a (Figure ). 2 a shows a double‐concave structure with an electron‐deficient inner core owing to the presence of peripheral chlorines, and thus 2 a is both geometrically and electronically suitable for assembly with electron‐rich buckybowls. As expected, 1 H NMR measurement indicated that mixing 1 with equimolar 2 a in solution caused its sole proton signal (H a ) to shift upfield by 0.11 ppm (Figure ).…”

“…However, this requires structural modification of the buckybowl and could affect its ability to undergo bowl inversion . On the other hand, the electron deficiency of 2 can be weakened by enhancing the electron‐donating ability of its peripheral anilino groups without altering its inner core geometry . In our current study, as the electron deficiency of the nanographene core decreases from 2 a to 2 d , the NMR shift of the complexed 1 relative to that of pure 1 also decreases from 0.11 to 0.08 ppm (Figure ).…”