Synthesis of corannulene-based nanographenes

Ezzah M. Muzammil, Dzeneta Halilovic, Mihaiela C. Stuparu
2019 Communications Chemistry  
Corannulene (C 20 H 10 ) is a polycyclic hydrocarbon in which five six-membered rings surround a central five-membered ring to construct a bowl-like aromatic structure. Here we examine the development of synthetic strategies that allow for the growth of the peripheral aromatic rings as a means to extend the aromatic area of the central corannulene nucleus and provide access to unique nanocarbon molecules. s p 2 -hybridised structures of carbon have fascinated the research community for a very
more » ... munity for a very long time. In 1985, buckminsterfullerene, otherwise known as C 60 , was discovered ( Fig. 1a) 1 . In this ball-shaped molecule, the curvature in the structure stems from the presence of fivemembered rings. In 1991, carbon nanotubes arrived on the scene 2 . Here, the structure is cylindrical and composed of only rolled-up six-membered rings. In 2004, a sheet-like single layer from graphite-graphene-was isolated 3 . All of these materials were shown to have extraordinary electronic and mechanical properties due to their unique curved or planar sp 2 -hybridised aromatic structures. Inspired by these discoveries, chemists have been developing strategies to access such aromatic hydrocarbons through rational ('bottom-up') synthetic approaches. Scott's 12-step chemical synthesis of fullerene C 60 from a rationally designed precursor is a testament to the ingenuity and resourcefulness of organic chemists 4 . In planar structures, nanographenes (well-defined cutouts of graphene with nano-scale dimensions) can now be prepared on a regular basis with a very diverse portfolio 5 . It is expected that combining the planar structure of graphene with the curvature of fullerenes may produce hybrid materials with interesting properties 6-8 . To induce non-planarity into nanographenes, a practical approach would be to introduce a fivemembered ring such as in the case of fullerene, C 60 . A perfect building block that allows for such a structural arrangement to happen is corannulene (1)-a molecule in which five six-membered rings surround a central five-membered ring to give a bowl-like structure (Fig. 1b) [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] . Corannulene also offers many beneficial features as a molecular building block. It has high solubility in common organic solvents. It can be derivatized in a well-defined manner. Due to synthetic ease, the derivatives can be prepared on a multigram scale. These attributes are important as they allow for the scalable preparation of carefully designed corannulene-based building blocks and the subsequent synthesis, purification and structural analysis of the larger (fused) aromatic systems. Recently, therefore, there has been a surge in employment of corannulene as a core molecule in the synthesis of extended aromatic structures. Our aim in this review article is to discuss
doi:10.1038/s42004-019-0160-1 fatcat:trnocnc3m5aonfpxfelx55lydq