Chirality sensing and size discrimination of anions by macrotricyclic cyclen-disodium complexes

Abstract

Two macrotricyclic ligands composed of two face-to-face octadentate metal chelates were synthesized. These cage-shaped disodium complexes had special recognition ability for various counter anions. Specific chiral dicarboxylates bound to the complexes within the cavity and exhibited chirality induction properties. For instance, N-Boc-Asp dianion strongly induced circular dichroism (CD) signals, but N-Boc-Glu dianion, which is one carbon longer, did not. Chirality on Na+: The first example of chirality sensing on Na+ was achieved by a macrotricyclic host composed of two octadentate cyclen-Na+ complexes. Chiral N-Boc-Asp dianions coordinated to the Na+ at the cavity, resulting in the chirality induction of the cage molecule, but N-Boc-Glu dianion, which is one carbon longer, did not.