Although higher fullerenes (HFU; &gt;C70)1 remain the focus of widespread interest across the scientific community, their study is still hampered not only by their relative scarcity in soot, but also by their tedious isolation and purification processes; indeed, efforts are always being made to develop extraction methods that do not rely on the (undesirable) use of chromatography.2 In this respect, de Mendoza and collaborators reported an elegant HFU separation technique,3,4 based on self-assembled molecular capsules of concave cyclotriveratrylene (CTV), bearing three hydrogen-bonding ureidopyrimidinone units (UPy); these species are particularly selective in encapsulating C70 and C84, which may then be easily retrieved by cleaving the hydrogen bonds holding the capsules together. In this communication, we present and discuss our computational efforts to understand the molecular basis of such selectivity. Using density functional theory (BP86/TZP), with crucial D3 dispersion corrections to treat capsule-fullerene interactions, we investigate several capsule conformers: either empty; or enclosing different HFU guests. Preference for C70 and C84 over C60 is convincingly confirmed: in those cases, the total energetic gain afforded by capsule formation and capsule-HFU interactions is large enough to overcome the cost of capsule deformation due to the presence of the guest. Moreover, the energetically preferred capsule conformer that we identify corresponds to the one also identified as such by NMR. (1) Diederich, F.; Ettl, R.; Rubin, Y.; Whetten, R. L.; Beck, R.; Alvarez, M.; Anz, S.; Sensharma, D.; Wudl, F.; Khemani, K. C.; Koch, A. Science 1991, 252, 548-551. (2) Zhang, C.; Wang, Q.; Long, H.; Zhang, W. J. Am. Chem. Soc. 2011, 133, 20995-21001. (3) Huerta, E.; Cequier, E.; de Mendoza, J. Chem. Commun. 2007, 5016-5018. (4) Huerta, E.; Metselaar, G. A.; Fragoso, A.; Santos, E.; Bo, C.; de Mendoza, J. Angew. Chem., Int. Ed. 2007, 46, 202-205.

Catching the big fullerene: Selectivity of self-assembled molecular capsules towards C70 and C84

251st National Meeting (2016)

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