Molecular basis for the recognition of higher fullerenes into ureidopyrimidinonecyclotriveratrylene self-assembled capsules

Abstract

Fullerenes C60, C70, and C84 may be readily encaged within a hydrogen-bonded dimeric capsule, based on two concave cyclotriveratrylene (CTV) scaffolds each bearing three self-complementary 2-ureido-4-[1H]-pyrimidinone (UPy) subunits. We herein report NMR and CD studies-complemented by dispersion-corrected density functional theory calculations-aiming to characterize such capsulefullerene complexes both structurally and energetically. Six fullerenes are considered: in agreement with experiment, calculations find that encapsulation is most favorable for C84 (on a par with C90), and follows the trend C60<C70<C76<C78<C84≈C90. As also found by NMR, the most stable capsules are formed by monomers of identical stereochemistry; with UPy and the CTV's OMe groups in mutual anti orientation; and UPy-CTV ethylene linkers within the capsular surface plane. Up to C78, encapsulation is favored by increasing host-guest contacts, but the trend is thereafter increasingly inhibited by growing capsule strain.

Molecular Basis for the Recognition of Higher Fullerenes into Ureidopyrimidinone–Cyclotriveratrylene Self‐Assembled Capsules

“…[18] Coordinatesofa ll optimized fullerene@1 2 structures are also available in the Supporting Information (all calculations reported herein are also entirely available online). [24] For the higherf ullerenes C 76 ,C 78 ,a nd C 84 ,w ec hose the isomers that are reported to have the highest experimental abundance: [25] D 2 (one enantiomer only), [24] C 2v ,a nd D 2 respectively. In the case of C 90 ,w ec hose the D 5h isomer in virtue of its highers ymmetry;w ea lso note that this is the mosta bundant C 90 isomer occurringi ns oot generated from Sm 2 O 3 -doped graphite rods.…”