Uncommon isonicotinamide supramolecular synthons in copper(II) complexes directed by nitrate and perchlorate anions

The title compounds, trans‐diaquabis(nitrato‐κO)bis(pyridine‐4‐carboxamide‐κN¹)copper(II), [Cu(NO₃)₂(C₆H₆N₂O)₂(H₂O)₂], (I), and trans‐diaquatetrakis(pyridine‐4‐carboxamide‐κN¹)copper(II) bis(perchlorate), [Cu(C₆H₆N₂O)₄(H₂O)₂](ClO₄)₂, (II), are composed of mononuclear coordination entities involving Cu^II ions and isonicotinamide. In (I), the centrosymmetric tetragonally distorted octahedral copper(II) environment contains trans‐related isonicotinamide and water molecules in the equatorial plane and two nitrate ions occupying the axial sites. In (II), the equatorial plane of the C₂‐symmetric distorted octahedron is built up of four isonicotinamide ligands, while water molecules occupy the axial positions. The complex molecules of (I) and (II) are linked into three‐dimensional supramolecular frameworks by O—H...O and N—H...O hydrogen bonds. The nitrate and perchlorate ions are building blocks that disturb the robust R₂²(8) amide supramolecular motif commonly found in crystal structures of copper–isonicotinamide complexes.