Complexes of NiX2 (X = Cl− and NO3−) with a NNO donor Schiff base: Anion dependent structural variations and spectroscopic behaviour

Two new nickel(II) complexes, [NiL(H2O)2Cl] (1) and [{NiLL′(H2O)}2(μ-H)]NO3·H2O (2), have been synthesized using a tridentate Schiff base ligand, HL, 2-[(2-dimethylamino-ethylimino)-methyl]-phenol, along with Cl− or NO3− as an anionic co-ligand or counter anion (where L′H = salicylaldehyde). Both complexes have been characterized by X-ray crystallography. The structural analyses reveal that complex 1 is mononuclear whereas 2 is a hydrogen-bridged dinuclear complex. The Ni(II) ions possess a distorted octahedral geometry in both structures. Both complexes show negative solvatochromic behaviour with increasing donor number (DN) of the solvent. In more coordinating solvents, like DMSO or methanol, the colour of the solutions is green, whereas in less coordinating solvents, like dichloromethane (DCM) or acetonitrile, it is red.

Graphical abstractThe structural analysis of two new nickel(II) complexes, [NiL(H2O)2Cl] (1) and [{NiLL′(H2O)}2(μ-H)]NO3·H2O (2) of a tridentate Schiff base ligand, HL, 2-[(2-dimethylaminoethylimino)-methyl]-phenol, along with Cl− or NO3− as an anionic co-ligand or counter anion reveals that the Ni(II) ions possess a distorted octahedral geometry in both complexes. Complex 1 is mononuclear whereas 2 is a mixed ligand, hydrogen bonded dinuclear species. Both complexes show negative solvatochromic behaviour with increasing donor number (DN) of the solvent.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Syntheses and crystal structures of two Ni(II) complexes with a tridentate NNO donor Schiff base ligand. ► Both complexes possess a distorted octahedral geometry around Ni(II). ► Both complexes show negative solvatochromic behaviour with increasing donor number (DN) of the solvents.