Metal complexation of calix[4]azacrown derivatives - Evidence for communication between upper and lower functionalised rims

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 bridging ligand, is also reported. The calix[4]arene framework consists of a bipyridyl unit connected at the upper rim of the calix[4]arene, through an amide linkage, and an azacrown unit at the lower rim, also connected through amide groups.