Two zinc(II) complexes containing a flexible double betaine, namely [{Zn(L)Br2}n]·nH2O (1) and [{Zn(L)2(H2O)2}n](ClO4)2n·4nH2O (2) [L=1,4-diazoniabicyclo [2.2.2]octane-1,4-diacetate,−O2CCH2N+(CH2CH2)3N+CH2CO2−], have been prepared and shown to have polymeric structures by single-crystal X-ray analysis. Complex (1) exhibits an infinite zigzag chain in which each zinc(II) atom is coordinated by two unidentate carboxylate oxygen atoms and two bromide ligands in a distorted tetrahedral geometry. Complex (2) consists of an assembly of catonic Zn(L)2(H2O)22+ moieties and discrete perchlorate anions as well as lattice water molecules. In (2) each zinc(II) atom is coordinated by two pairs of unidentate carboxylate oxygen atoms and two aqua ligands in a distorted octahedral geometry and cross-linked by skeletons of double betaine ligands to form a corrugated layer structure corresponding to the plane (100).