{5,5'-Dihydr-oxy-2,2'-[o-phenyl-enebis-(nitrilo-methyl-idyne)]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 tetra-dentate Schiff base ligand. The Ni atom lies on a crystallographic twofold rotation axis. The asymmetric unit contains one half-mol-ecule of the complex and a water mol-ecule. An inter-molecular 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 mol-ecule. In the crystal structure, mol-ecules are linked by π-π stacking inter-actions, with centroid-centroid distances in the range 3.5750†(11)-3.7750†(11)†à . 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 hydroxy-phenyl rings is 13.16†(5)°. In the crystal structure, mol-ecules are linked into infinite one-dimensional chains by directed four-membered O-H⋯O-H inter-actions along the c axis and are further connected by C-H⋯O and π-π stacking into a three-dimensional network. An inter-esting feature of the crystal structure is the short Ni⋯O, O⋯O and N⋯N inter-actions which are shorter than the sum of the van der Waals radii of the relevant atoms. The crystal structure is stabilized by inter-molecular O-H⋯O and C-H⋯O hydrogen bonds and by π-π stacking inter-actions.