Encapsulation of Small Gas Molecules by Cryptophane-111 in Organic Solution. 1. Size- and Shape-Selective Complexation of Simple Hydrocarbons - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases Année : 2009

Encapsulation of Small Gas Molecules by Cryptophane-111 in Organic Solution. 1. Size- and Shape-Selective Complexation of Simple Hydrocarbons

Kathleen E. Chaffee
  • Fonction : Auteur
Heather A. Fogarty
  • Fonction : Auteur
Thierry Brotin
Boyd M. Goodson
  • Fonction : Auteur
Jean-Pierre Dutasta

Résumé

The reversible trapping of small hydrocarbons and other gases by cryptophane-111 (1) in organic solution was characterized with variable-temperature 1H NMR spectroscopy. Characteristic spectral changes observed upon guest binding allowed kinetic and thermodynamic data to be readily extracted, permitting quantification and comparison of different host−guest interactions. Previous work (J. Am. Chem. Soc. 2007, 129, 10332) demonstrated that 1, the smallest cryptophane to date, forms a complex with xenon with remarkably high affinity. Presently, it is shown that 1 also exhibits slow exchange dynamics with methane at reduced temperatures (δbound = −5.2 ppm) with an association constant Ka = 148 M−1 at 298 K. In contrast, ethane and ethylene are poorly recognized by 1 with Ka values of only 2 M−1 and 22 M−1, respectively; moreover, chloromethane (whose molecular volume is similar to that of xenon, ∼42 Å3) is not observed to bind to 1. Separately, molecular hydrogen (H2) gas is observed to bind 1, but in contrast to other ligands presently studied, H2 complexation is spectrally manifested by fast exchange throughout virtually the entire range of available conditions, as well as by a complex dependence of the guest 1H resonance frequency upon temperature and host concentration. Taken together, these results establish 1 as a selective host for small gases, with implications for the design of size- and geometry-selective sensors targeted for various gas molecules.
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hal-01116892 , version 1 (15-02-2015)

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Kathleen E. Chaffee, Heather A. Fogarty, Thierry Brotin, Boyd M. Goodson, Jean-Pierre Dutasta. Encapsulation of Small Gas Molecules by Cryptophane-111 in Organic Solution. 1. Size- and Shape-Selective Complexation of Simple Hydrocarbons. Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 2009, 113 (49), pp.13675-13684. ⟨10.1021/jp903452k⟩. ⟨hal-01116892⟩
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