{5,5′-Dihydroxy-2,2′-[o-phenylenebis(nitrilomethylidyne)]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 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 R12(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.