Pure C-H Hydrogen Bonding to Ghloride Ions: A Preorganized and Rigid Macrocyclic Receptor

摘要

Anions play important chemical and biological roles, and the supramolecular chemistry involving them has grown accordingly. These developments range from fundamental studies on noncovalent bonding to the design of anion receptors and anion assistance to asymmetric catalysis. A substantial number of artificial organic hosts for anions incorporate strong hydrogen bonds (H-bonds), usually N-H···X~-, e.g., calixpyrrole, or if C-H···X~- H bonds are used, the carbon atom is adjacent to a cationic center, e.g., imidazolium. The strength and the relative significance of weak C-H···X~- H bonds originating from neutral ring systems has been examined recently. Although stronger than previously thought, these H-bonds were only considered as "additional binding sites within a host cavity."