{5,5′-Dihydr-oxy-2,2′-[o-phenyl-enebis-(nitrilo-methyl-idyne)] diphenolato}nickel(II) dihydrate

Abstract

In the title complex, [Ni(C20H14N2O4)]·2H2O, the NiII ion is in an essentially square-planar geometry involving an N2O2 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) 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 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.