Polarizing a Hydrophobic Cavity for the Efficient Binding of Organic Guests: The Case of Calix[6]tren, a Highly Efficient and Versatile Receptor for Neutral or Cationic Species
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- 作者：Ulrich Darbost ; Marie-Noë ; lle Rager ; Samuel Petit ; Ivan Jabin ; and Olivia Reinaud
- 刊名：Journal of the American Chemical Society
- 出版年：2005
- 出版时间：June 15, 2005
- 年：2005
- 卷：127
- 期：23
- 页码：8517 - 8525
- 全文大小：279K
- 年卷期：v.127,no.23(June 15, 2005)
- ISSN：1520-5126
文摘
The host-guest properties of calix[6]tren 1 have been evaluated. The receptor is based on acalix[6]arene that is covalently capped at the narrow rim by a tren unit. As a result, the system presents aconcave hydrophobic cavity with, at its bottom, a grid-like nitrogenous core. Despite its well-defined cavityand opening to the outside at the large rim, 1 did not behave as a good receptor for neutral molecules inchloroform. However, it exhibited efficient endo-complexation of ammonium guests. By contrast, the per-protonated host, 1.4H+, behaved as a remarkable receptor for small organic molecules. The complexationis driven by a strong charge-dipole interaction and hydrogen bonds between the polar guest and thetetracationic cap of the calixarene. Finally, coordination of Zn2+ to the tren core led to the asymmetrizationof calixarene cavity and to the strong but selective endo-binding of neutral ligands. This study emphasizesthe efficiency of a receptor presenting a concave hydrophobic cavity that is polarized at its bottom. Theresulting combination of charge-dipole, hydrogen bonding, CH-
, and van der Waals interactions highlystabilizes the supramolecular architectures. Also, importantly, the tren cap allows the tuning of thepolarization, offering either a basic (1), a highly charged and acidic (1.4H+), or a coordination (1.Zn2+) site.As a result, the system proved to be highly versatile, tunable, and interconvertible in solution by simpleaddition of protons, bases, or metal ions.
, and van der Waals interactions highlystabilizes the supramolecular architectures. Also, importantly, the tren cap allows the tuning of thepolarization, offering either a basic (1), a highly charged and acidic (1.4H+), or a coordination (1.Zn2+) site.As a result, the system proved to be highly versatile, tunable, and interconvertible in solution by simpleaddition of protons, bases, or metal ions.