Molecular Basis for the Recognition of Higher Fullerenes into Ureidopyrimidinone–Cyclotriveratrylene 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.

Cucurbit[n]urils‐related Multitopic Supramolecular Components: Design, Properties, and Perspectives

“…Recently, interesting example of capsules consisting of two complementary hemispheres held together via either halogen [36] or hydrogen [37] bonds have been reported. The importance of these lateral interactions can be demonstrated on an example of molecular capsules.…”

Complexation Between (O‐Methyl)6‐2,6‐Helic[6]arene and Tertiary Ammonium Salts: Acid/Base‐ or Chloride‐Ion‐Responsive Host–Guest Systems and Synthesis of [2]Rotaxane

“…Macrocyclic arenes including calixarenes, resorcinarene, cyclotriveratrylene, pillararenes, and their analogues have become one of the most studied synthetic macrocyclic hosts in recent decades. It is known that pillararenes can form complexes with quaternary ammonium salts mainly by cation⋅⋅⋅π interactions, and calix[6]arene derivatives can complex with secondary ammonium salts .…”

Self-assembled Cages and Capsules Using Cyclotriveratrylene-type Scaffolds

“…Activation energies for racemization are of the order of 24 26.5 kJ mol ¹1 . 4,5 Racemic mixtures of both enantiomers are most often used, though the enantiomers can be separated.…”

“…19 Homodimeric capsules of type (2) 2 ¢F, where 2 is a tris(4-ureidopyrimidinone)-appended CTG and F is an encapsulated fullerene, have been reported by de Mendoza and co-workers (Chart 3). 5,20,21 Binding of the fullerene templates the capsule formation in solution. The system is selective for higher fullerenes and a combination of experimental and theoretical studies 5,21 have established that binding constants follow the trend C 90 µ C 84 > C 78 > C 76 > C 70 > C 60 .…”

“…5,20,21 Binding of the fullerene templates the capsule formation in solution. The system is selective for higher fullerenes and a combination of experimental and theoretical studies 5,21 have established that binding constants follow the trend C 90 µ C 84 > C 78 > C 76 > C 70 > C 60 . This has potential utility in the purification of higher fullerenes given that fullerene can be recovered from the (2) 2 ¢F adduct through a change in solvent polarity.…”