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1. Design and recognition of cucurbituril-secured platinum-bound oligopeptides

   https://doi.org/10.1039/d1sc02637b  

   Barbero, Héctor; Masson, Eric (July 2021, Chemical Science)

   null (Ed.)

   Platinum terpyridyl complexes, stacked on top of one another and secured as dimers with cucurbit[8]uril (CB[8]) in aqueous medium, were functionalized quantitatively and in situ with a pair of pentapeptides Phe-(Gly) 3 -Cys by grafting their cysteine residues to the Pt centers. The resulting CB[8]·(Pt·peptide) 2 assemblies were used to target secondary hosts CB[7] and CB[8] via their pair of phenylalanine residues, again in situ . A series of well-defined architectures, including a supramolecular “pendant necklace” with hybrid head-to-head and head-to-tail arrangements inside CB[8], were obtained during the self-sorting process after combining only 3 or 4 simple building units. 

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2. Selective Separation of Hexachloroplatinate(IV) Dianions Based on Exo‐Binding with Cucurbit[6]uril

   https://doi.org/10.1002/anie.202104646  

   Wu, Huang; Wang, Yu; Jones, Leighton_O; Liu, Wenqi; Zhang, Long; Song, Bo; Chen, Xiao‐Yang; Stern, Charlotte_L; Schatz, George_C; Stoddart, J_Fraser (June 2021, Angewandte Chemie International Edition)

   Abstract The recognition and separation of anions attracts attention from chemists, materials scientists, and engineers. Employing exo‐binding of artificial macrocycles to selectively recognize anions remains a challenge in supramolecular chemistry. We report the instantaneous co‐crystallization and concomitant co‐precipitation between [PtCl₆]²⁻dianions and cucurbit[6]uril, which relies on the selective recognition of these dianions through noncovalent bonding interactions on the outer surface of cucurbit[6]uril. The selective [PtCl₆]²⁻dianion recognition is driven by weak [Pt−Cl⋅⋅⋅H−C] hydrogen bonding and [Pt−Cl⋅⋅⋅C=O] ion–dipole interactions. The synthetic protocol is highly selective. Recognition is not observed in combinations between cucurbit[6]uril and six other Pt‐ and Pd‐ or Rh‐based chloride anions. We also demonstrated that cucurbit[6]uril is able to separate selectively [PtCl₆]²⁻dianions from a mixture of [PtCl₆]²⁻, [PdCl₄]²⁻, and [RhCl₆]³⁻anions. This protocol could be exploited to recover platinum from spent vehicular three‐way catalytic converters and other platinum‐bearing metal waste. 

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3. Supramolecular self-sorting predicted by a simple harmonic oscillator model

   https://doi.org/10.1039/D4CC05336B  

   Sacristán-Martín, Adriana; Álvarez-Llorente, Nerea; Masson, Eric; Diez-Varga, Alberto; Barbero, Héctor (November 2024, Chemical Communications)

   The self-sorting process of homobimetallic Pt(ii) terpyridyl acetylide dimers secured by a pair of Cucurbit[8]uril macrocycles with recognition motif mismatch can be quantified using a model comprising two coupled harmonic oscillators. 

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4. Self-assembled, optically-active {naphthalene diimide}U{cucurbit[8]uril} ensembles in an aqueous environment

   https://doi.org/10.1039/d1cp00659b  

   Higginbotham, Heather F.; Maniam, Subashani; Hsia, Tina; Isaacs, Lyle; Langford, Steven J.; Bell, Toby D. (January 2021, Physical Chemistry Chemical Physics)

   null (Ed.)

   Naphthalene diimides (NDIs) are shown to arrange spontaneously co-facially with cucurbit[8]uril (CB[8]) in an aqueous environment through purely non-covalent interactions. The resultant 2 : 2 supramolecular complex of NDI and CB[8] is highly fluorescent (>30 times more than the constituent NDIs) due to the formation of NDI–NDI excimers within the supramolecular complex. 

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5. Cucurbiturils mimicked by low polarizability solvents with pre-formed cavities: an empirical model to predict hydrocarbon selectivity

   https://doi.org/10.1039/D1SC06728A  

   Nazimuddin, Md; Barbero, Héctor; Rabbani, Ramin; Masson, Eric (April 2022, Chemical Science)

   Relative binding affinities of a series of nine rigid hydrocarbons towards the cavity formed by a portion of the inner wall of cucurbit[8]uril (CB[8]) and a positive auxiliary guest were determined by competitive 19 F NMR titrations in deuterium oxide. The corresponding free binding energies were corrected by the hydrocarbon computed solvation energies to obtain their free energies of transfer from the gas phase to the CB[8]/auxiliary guest cavity. These energies correlate linearly with the hydrocarbon static polarizabilities, thereby suggesting that the selectivity is driven, perhaps exclusively, by dispersive interactions between the hydrocarbons and the tailor-made cavity, regardless of the degree of unsaturation of the guests. The free energies of transfer also correlate linearly with the energy released upon introduction of the hydrocarbon into a pre-formed cavity extruded from a solvent (benzene) selected to mimic the polarity and polarizability of the CB[8]/auxiliary probe cavity – and this, with a unity slope. Among other features, this empirical model also accurately predicts the relative binding affinities of various rigid hydrocarbons to CB[6] and CB[7], as well as noble gases to CB[5], when the macrocycles are mimicked with pre-formed cavities in perfluorohexane or perfluorohexane/benzene mixtures, both being notoriously non-polar and non-polarizable environments. 

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