{5,5′-Dihydr­oxy-2,2′-[o-phenyl­enebis­(nitrilo­methyl­idyne)]diphenolato}nickel(II) dihydrate

In the title complex, [Ni(C(20)H(14)N(2)O(4))]·2H(2)O, the Ni(II) ion is in an essentially square-planar geometry involving an N(2)O(2) atom set of the tetra­dentate Schiff base ligand. The Ni atom lies on a crystallographic twofold rotation axis. The asymmetric unit contains one half-mol­ecule of the complex and a water mol­ecule. An inter­molecular O—H⋯O hydrogen bond forms a four-membered ring, producing an R (1) (2)(4) ring motif involving a bifurcated hydrogen bond to the phenolate O atoms of the complex mol­ecule. In the crystal structure, mol­ecules are linked by π–π stacking inter­actions, with centroid–centroid distances in the range 3.5750 (11)–3.7750 (11) Å. As a result of the twofold symmetry, the central benzene ring makes the same dihedral angle of 15.75 (9)° with the two outer benzene rings. The dihedral angle between the two hydroxy­phenyl rings is 13.16 (5)°. In the crystal structure, mol­ecules are linked into infinite one-dimensional chains by directed four-membered O—H⋯O—H inter­actions along the c axis and are further connected by C—H⋯O and π–π stacking into a three-dimensional network. An inter­esting feature of the crystal structure is the short Ni⋯O, O⋯O and N⋯N inter­actions which are shorter than the sum of the van der Waals radii of the relevant atoms. The crystal structure is stabilized by inter­molecular O—H⋯O and C—H⋯O hydrogen bonds and by π–π stacking inter­actions.