The unanti­cipated oxidation of a tertiary amine in a tetra­cyclic glyoxal-cyclam condensate yielding zinc(II) coordinated to a sterically hindered amine oxide

The crystal structure of the first reported glyoxal–tetra­aza­macrocycle condensate amine oxide is presented. The sterically hindered oxidized amine binds zinc(II) through the oxygen atom in its folded cleft, with an inter­nal hydrogen bond across the cleft between the oxygen and a protonated tertiary nitro­gen.