Isotypic MnII and FeII binuclear complexes of the ligand 5,6-bis­­(pyridin-2-yl)-pyrazine-2,3-di­carb­­oxy­lic acid

The title isotypic complexes, bis­[μ-5,6-bis­(pyridin-2-yl)pyrazine-2,3-di­carboxylato]-κ4N1,O2,N6:O3;κ4O3:N1,O2,N6-bis­[di­aqua­manganese(II)] tetra­hydrate, [Mn2(C16H8N4O4)2(H2O)4]·4H2O, (I), and bis­[μ-5,6-bis­(pyridin-2-yl)pyrazine-2,3-di­carboxyl­ato]-κ4N1,O2,N6:O3;κ4O3:N1,O2,N6-bis­[di­aqua­iron(II)] tetrahydrate, [Fe2(C16H8N4O4)2(H2O)4]·4H2O, (II), are, respectively, the mangan­ese(II) and iron(II) complexes of the ligand 5,6-bis­(pyridin-2-yl)-pyrazine-2,3-di­carb­oxy­lic acid. The complete mol­ecule of each complex is generated by inversion symmetry. Each metal ion is coordinated by a pyrazine N atom, a pyridine N atom, two carboxyl­ate O atoms, one of which is bridging, and two water O atoms. The metal atoms have MN2O4 coordination geometries and the complexes have a cage-like structure. In the crystals of both compounds, the complexes are linked by O—H⋯O and O—H⋯N hydrogen bonds involving the coordinating water mol­ecules, forming chains along [100]. These chains are linked by O—H⋯O hydrogen bonds involving the non-coordinating water mol­ecules, forming layers parallel to (011). The layers are linked by pairs of C—H⋯O hydrogen bonds and offset π–π inter­actions, so forming a hydrogen-bonded three-dimensional framework