Bis(9-amino-acridinium) bis-(pyridine-2,6-dicarboxyl-ato-κO,N,O)nickelate(II) trihydrate.

The title compound, (C(13)H(11)N(2))(2)[Ni(C(7)H(3)NO(4))(2)]·3H(2)O, consists of a mononuclear anionic complex, two 9-amino-acridinium cations and three uncoordinated water mol-ecules. Two pyridine-2,6-dicarboxyl-ate (pydc) ligands are bound to the Ni(II) ion, giving an NiN(2)O(4) bonded set. The coordination geometry around the Ni(II) atom is distorted octa-hedral. There are two types of robust O-H⋯O hydrogen-bond synthons, namely R(6) (6)(24) and R(2) (4)(8), which link the complex anions and water mol-ecules to each other. N-H⋯O hydrogen bonds connect the stacks of anions and cations in the structure. Other inter-molecular inter-actions, including weak C-H⋯O hydrogen bonds, π-π [shortest centroid-centroid distance = 3.336†(7)†à ] and C-O⋯π [O⋯centroid distance = 3.562†(10)†à ] inter-actions, connect the various components.