Cadmium nitrate coordination polymers with substituted pyridazino[4,5‐d]pyridazines

catena‐Polyaquabis(nitrato‐κ²O,O′)cadmium(II)]‐μ‐1,2,3,6,7,8‐hexa­hydro­cinnolino5,4,3‐cde]cinnoline‐κN¹:κN⁶], Cd(NO₃)₂(C₁₂H₁₂N₄)(H₂O)]_n, (I), and catena‐polybis(nitrato‐κ²O,O′)cadmium(II)]‐μ‐2,2,7,7‐tetra­methyl‐1,2,3,6,7,8‐hexahydro­cinnolino5,4,3‐cde]cinnoline‐κN¹:κN⁶] chloro­form solvate], {Cd(NO₃)₂(C₁₂H₁₂N₄)]·CHCl₃}_n, (II), are the first structurally examined cadmium–pyridazine coordination compounds. They possess one‐dimensional polymeric structures supported by the bidentate bridging function of the cinnolino5,4,3‐cde]cinnoline ligands, which lie about inversion centres. The Cd atoms are seven‐coordinated in (I) and six‐coordinated in (II), involving two bidentate nitrate groups Cd—O = 2.229 (2)–2.657 (2) Å], two N atoms of the cinnoline ligands Cd—N = 2.252 (2)–2.425 (2) Å], and, additionally, a water O atom in (I) Cd—O = 2.284 (2) Å]. In (I), the coordinated organic and aqua ligands form an intra­molecular O—H?N hydrogen bond O?N = 2.730 (3) Å].