Synthesis and Characterization of New Reinforced Pentaaza Macrobicyclic and Bis(macrobicyclic) Copper(II) Complexes

The dinuclear bis(macrocyclic) complexes [Cu2(4)]4+ and [Cu2(5)]4+ as well as the mononuclear copper(II) complexes of 3a-3c can be prepared by the metal-template condensation involving 1,4-bis(3-aminopropyl)piperazine and formaldehyde. This work supports the suggestion that their decomposition reaction rates in acidic aqueous solutions are strongly influenced by the steric factors of the N-alkyl groups, even though the alkyl groups are attached to the uncoordinated nitrogen atoms.6 This work also shows that the ligand field strength and chemical properties of the copper(II) complexes are strongly influenced by the position of the additional -(CH2)2- linkage. To our knowledge, [Cu 2(4)]4+ and [Cu2(5)]4+ are very rare examples of 15-membered pentaaza macrocyclic complexes that are relatively inert against decomposition even in concentrated HClO4 solutions.