The magnesium complex (1) of the tetranucleating macrocyclic ligand H4L1 on transmetalation with copper(II) perchlorate in the presence of triethylamine produces the dicopper(II) complex (3) of the dinucleating macrocyclic ligand H2L3, while the same reaction when carried out in absence of triethylamine affords the metal-deficient compound (4) derived from H2L3.