Enantiopure trigonal bipyramidal coordination cages templated by in situ self-organized D2h-symmetric anions

Abstract

The control of a molecule’s geometry, chirality, and physical properties has long been a challenging pursuit. Our study introduces a dependable method for assembling D₃-symmetric trigonal bipyramidal coordination cages. Specifically, D_2h-symmetric anions, like oxalate and chloranilic anions, self-organize around a metal ion to form chiral-at-metal anionic complexes, which template the formation of D₃-symmetric trigonal bipyramidal coordination cages. The chirality of the trigonal bipyramid is determined by the point chirality of chiral amines used in forming the ligands. Additionally, these cages exhibit chiral selectivity for the included chiral-at-metal anionic template. Our method is broadly applicable to various ligand systems, enabling the construction of larger cages when larger D_2h-symmetric anions, like chloranilic anions, are employed. Furthermore, we successfully produce enantiopure trigonal bipyramidal cages with anthracene-containing backbones using this approach, which would be otherwise infeasible. These cages exhibit circularly polarized luminescence, which is modulable through the reversible photo-oxygenation of the anthracenes.

The control of a molecule’s geometry, chirality, and physical properties has long been a challenging pursuit. Here the authors introduce a method for assembling D₃-symmetric trigonal bipyramidal coordination cages which exhibit chiral selectivity for the included chiral-at-metal anionic template.