Three zinc(II) complexes presenting a ZnN₆ chromophore and with peroxodi­sulfate as the counter-ion

The crystal structures of three Zn complexes with the peroxodi­sulfate anion (pds²⁻) acting as counter-ion are reported, namely bis(2,2′:6′,2′′-ter­pyridine-κ³N)­zinc(II) hexa­oxo-μ-peroxo-di­sulfate(VI) dihydrate N,N-di­methyl­form­amide solvate, [Zn(C₁₅H₁₁N₃)₂](S₂O₈)·2H₂O·C₃H₇NO or [Zn(tpy)₂](pds)·2H₂O·DMF, (I), bis­[2,4,6-tris(2-pyridyl)-1,3,5-triazine-κ²N²,N⁴]­zinc(II) hexaoxo-μ-peroxo-di­sulfate(VI) dihydrate, [Zn(C₁₈H₁₂N₆)₂](S₂O₈)·2H₂O or [Zn(tpt)₂](pds)·2H₂O, (II), and bis­[2,6-bis(1H-benzimidazol-2-yl-κN³)­pyridine]­zinc(II) hexaoxo-μ-peroxo-di­sulfate(VI) N,N-di­methyl­form­amide trisolvate, [Zn(C₁₉H₁₃N₅)₂](S₂O₈)·3C₃H₇NO or [Zn(bbp)₂](pds)·3DMF, (III), where tpy is 2,2′:6′,2′′-ter­pyridine, tpt is 2,4,6-tris(2-pyridyl)-1,3,5-triazine, bbp is 2,6-bis(1H-benz­imidazol-2-yl)­pyridine and DMF is N,N-di­methyl­form­amide. The three structures are monomeric and present the Zn cation in a distorted octahedral environment, defined by two chelating tricoordinated ligands at almost right angles to each other. These cationic entities interact with an anionic network composed of hydrogen-bonded pds²⁻ anions and solvate water and DMF mol­ecules via Coulombic forces, and with each other through a number of π–π and C=C⋯π contacts connecting the aromatic rings. The pds²⁻ anions stabilize the structures in unprecedented counter-ion behaviour.