Synthetic Chiral Carbon Nanoforms
Chirality is an important and fascinating concept which, however, has not been properly addressed in nanocarbons science.1 Previous results from our group support the basic idea that the chemistry of fullerenes, as probably the most studied carbon nanostructure from a synthetic point of view, is not fully developed. A variety of fundamental reactions – mainly involving transition metals and organocatalysts – have allowed us addressing issues such as regio- and stereo-selectivity in the fullerenes functionalization.2
Chirality in graphene and, more specifically, in graphene quantum dots (GQDs), has also been almost neglected despite the interest for further applications. In particular, when considering the potential applications of GQDs, chirality is an important aspect that can severely influence their performance and that has not been addressed so far. We have recently proven the principle that chiral graphene quantum dots (CGQDs) can be obtained by reaction of oxidized GQDs with enantiomerically pure (R) or (S)-2-phenyl-1-propanol and that their chirality transferred to the supramolecular assemblies formed with small molecules such as pyrene.3 Finally, as a proof of concept, we have recently published the synthesis and characterization of the first inherently chiral bilayer nanographene with a helicene linker, both as the racemate and the M isomer with 93% ee.4 By extending precedented helicene starting material, we obtained an unprecedented folded, chiral nanographene comprised of two hexa-peri-hexabenzocoronene layers fused to a helicene (Figure). The rigidity of the helicene linker forces the layers to adopt a nearly-aligned AA-stacked conformation rarely observed in few-layer graphene. In this communication, the aforementioned results as well as the most recent findings based on curved corannulene will be discussed.
1. E. E. Maroto, M. Izquierdo, S. Reboredo, J. Marco-Martínez, S. Filippone, N. Martín "Chiral Fullerenes from Asymmetric Catalysis" Acc. Chem. Res. 2014, 47, 2660−2670.
2. (a) Filippone, S., Maroto, E.E., Martín-Domenech, A., Suarez, M. and Martín, N., Nature Chem., 2009, 1, 578; (b) Maroto, E. E.; de Cozar, A.; Filippone, S.; Martin-Domenech, A.; Suarez, M.; Cossio, F. P.; Martín, N. Angew. Chem. Int. Ed., 2011, 50, 6060; (c) Sawai, K.; Takano, Y.; Izquierdo, M.; Filippone, S.; Martín, N.; Slanina, Z.; Mizorogi, N.; Waelchli, M.; Tsuchiya, T.; Akasaka, T.; Nagase, S. J. Am. Chem. Soc., 2011, 133, 17746; (d) Maroto, E.E., Filippone, S., Martín-Domenech, A., Suarez, M. and Martín, N., J. Am. Chem. Soc. 2012, 134, 12936; (e) E. E. Maroto, S. Filippone, M. Suárez, R. Martínez-Álvarez, A. de Cózar, F. P. Cossío, N. Martín, J. Am. Chem. Soc., 2014, 136, 705.
3. M. Vázquez-Nakagawa, L. Rodríguez-Pérez, M. A. Herranz, N. Martín, Chem. Commun., 2016, 52, 665-668. See also: N. Suzuki, Y. Wang, P. Elvati, Z.-B. Qu, K. Kim, S. Jiang, E. Baumeister, J. Lee, B. Yeom, J. H. Bahng, J. Lee, A. Violi, N. A. Kotov, ACS Nano 2016, 10, 1744-1755.
4.P. J. Evans, J. Ouyang, L. Favereau, J. Crassous, I. Fernández, J. Perles Hernáez, N. Martín, Angew. Chem. Int. Ed. 2018, 57, 6774 –6779.