Hydrogen bonding plays a crucial role in structuring highly-ordered proteins and networks of biomolecules. The rational design and synthesis of artificial supramolecular systems that are assembled with the aid of hydrogen bonding are interesting research targets, as well.
Fullerene consists of 60 sp2-hybridized carbon atoms, forming a closed shell. Chemical transformations can be used to create an orifice in C60 at which functional groups can be introduced. Based on this strategy, Yasujiro Murata, Kyoto University, Japan, and colleagues have synthesized two open-fullerenols that aggregate in a face-to-face dimeric configuration via intra- and intermolecular hydrogen bonding (example pictured).
The team reacted an open fullerene precursor with N-methylmorpholine N-oxide (NMO) to generate a tetracarbonyl intermediate via bond cleavage, which is then hydrolyzed to give one of the targeted open-fullerenols in a yield of 88 %. Starting from the same precursor, a reaction with singlet oxygen gave a second open-fullerenol in a yield of 10 %.
Both open-fullerenols have a bis(hemiketal) moiety and aggregate via hydrogen bonds to form a dimeric configuration. The hydroxy groups adopt a rhomboidal or chair-like arrangement as confirmed by X-ray diffraction analysis. Such precisely controlled arrangements of nanocarbon materials could be useful in a variety of applications, such as electronic materials or molecular delivery systems.
- Synthesis of Hydrogen‐Bonded Open‐Fullerenol Dimers,
Yoshifumi Hashikawa, Shumpei Sadai, Yasujiro Murata,