Abstract The coordination chemistry of calix [4] azacrowns obtained from the reaction of a diester calix [4] arene with diethylenetriamine provided unusual copper (II) and manganese (II) complexes in which calix [4] azacrown acts as a bidentate N, O-donor ligand, in some cases, but as a unidentate N-donor ligand, in other cases. The first example of a binuclear ruthenium (II)/manganese (II) complex, involving the calix [4] arene framework as the ...