Synthesis of corannulene-based nanographenes

Abstract

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 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) 9-20. 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

Geodesic‐Planar Conjugates: Substituted Buckybowls—Synthesis, Photoluminescence and Electrochemistry

“…[10,11] During the last decades the chemistry andp hysics of CA-derived buckybowl derivatives was thoroughlys tudied. [12][13][14][15][16][17][18] However,c omparably less work has been carried out in the field of Idpc and its derivatives.T he first synthetic approach towards Idpc by palladium catalyzed cyclization of suitable precursors was reported already in 2000, but lacked generality. [19] The aluminium-oxide mediated cove-regionr ing-closure through CÀF bond activation of fluoroarenes [20] towards pristine Idpc and other bowl-shaped PAHs developed by Amsharov et al in 2012 constituted am ajor breakthrough.…”

Corannulene‐Based Electron Acceptors: Combining Modular and Practical Synthesis with Electron Affinity and Solubility

“…Recently, there has been an impetus in the design and synthesis of non‐fullerene electron acceptors displaying high solubility, scalability, and ease of derivatization . Corannulene, with a recently developed kilogram‐scale synthesis, high solubility due to a lack of intermolecular π–π stacking interactions, and an adjustable structure is a suitable candidate for this purpose . Pristine corannulene, however, is not as good an electron acceptor as fullerene C 60 .…”

“…In this regard, fluorinated aromatic thiols can be accessed from commercial sources as precursors to sulfides. The complementary halogenated coupling partners are ubiquitous in corannulene chemistry . Corannulene imide, for instance, can be easily accessed with bromide functionalities .…”

as-Indaceno[3,2,1,8,7,6-ghijklm]terrylene as a near-infrared absorbing C70-fragment

“…Bowl-shaped aromatic hydrocarbons have been actively explored in modern organic chemistry 1 – 8 . Owing to their structural nonplanarity, these molecules exhibit intriguing characteristics such as high solubility, structural flexibility 9 – 14 , unique host–guest recognition 15 – 18 and high electronic conductivity 19 , 20 .…”