Anion control of the formation of geometric isomers in a triple helical array

Abstract

The amide-substituted unsymmetrical ligand L¹ upon coordination to Co²⁺ forms the dinuclear triple helicate [Co₂(L¹)₃]⁴⁺ which exists as both possible C₁ and C₃ symmetric geometric isomers in solution, however, upon addition of nitrate ions, the formation of an anion binding cavity is favoured and hence the sole product is the C₃ symmetric isomer in which all three amide substituents are hydrogen bonded to the nitrate anion.