The Cu(II) complex of a C-lipophilized 13aneN4 macrocycle with an additional protonable amino group as micellar anion receptor

Abstract

Three 13aneN4 macrocyclic ligands have been prepared bearing a -CH₂NHR side arm (R = H, n-C₅H₁₁, n-C₁₀H₂₁) on a carbon atom. When Cu²⁺ is complexed in the macrocyclic ring, the amino group of the side arm undergoes an acid–base protonation equilibrium but it is not able to coordinate apically the metal cation even when it is deprotonated. The Cu²⁺ complex with the ligand bearing the longest appended aliphatic chain is fully confined inside Triton X-100 micelles, and its ability to bind and sequestrate a series of anions inside micelles has been studied at two different pH values, i.e. both with protonated and neutral side-arm amino group. The favourable role played by the protonated amino group in the side arm has been demonstrated.