Synthesis, Structure, and Complexation of a Large 28-mer Macrocycle Containing Two Binding Sites for Either Anions or Metal Ions

The “one-pot” synthesis and characterization of a large 28-mer macrocycle (H4L2) with oxamido units capable of
complexing guest ions through oxygen or nitrogen donor atoms is reported. Single-crystal structure determination
of H8L2(NO3)4 and {Cu2[H2L2](H2O)2}(NO3)2 demonstrated that the macrocycle contains two sites capable of
complexing two nitrate anions or two copper(II) ions, involving a large structural reorganization in the conformation
of the macrocyclic framework on coordination of the copper(II) ions when compared to the nitrate. Electrochemical
and magnetic susceptibility measurements on the dinuclear Cu(II) complex and the related mononuclear and trinuclear
Cu(II) complexes derived from the related 14-mer macrocycle were carried out and illustrate the role of the oxamido
groups in mediating metal−metal interaction and delocalization.